Abstract: According to a method of measuring a thickness, to measure a thickness d of a liquid crystal layer 11, a property of reflected light is utilized, in that the light returns maintaining the same polarizing plane as that of an entrance when a polarizing plane-maintaining condition is satisfied in which a difference in optical path lengths between an ordinary ray and an extraordinary ray of the reflected light is a sum of an integer multiple of the wavelength and a half-wavelength or an integer multiple, to find a wavelength at which the polarizing plane-maintaining condition is satisfied. A reasonable &Dgr;n·d is thereby found. This is performed for a plurality of wavelengths to find a relational expression of a wavelength and &Dgr;n·d. A known combination of a wavelength &lgr; and &Dgr;n is assigned to the relational expression to find d.

Abstract: An object of the invention is to obtain achromatic display with high contrast and high lightness. A reflection type liquid crystal display device of NB mode comprises a liquid crystal cell having an STN type liquid crystal layer; a first phase difference plate; a second phase difference plate; a polarizing plate, the first and second phase difference plates and polarizing plate being disposed on one surface of the liquid crystal cell in this order; and a reflecting layer disposed in the liquid crystal cell, the reflecting layer forming the other surface of the liquid crystal cell. The liquid crystal layer retardation &Dgr;nLC.dLC, the first phase difference plate retardation &Dgr;n1.d1 and the second phase difference plate retardation &Dgr;n2.d2 are selected from the ranges of 660 nm to 830 nm, 120 nm to 240 nm and 300 nm to 430 nm, respectively. A twist angle &khgr; is selected from the range of 220° to 260°.

Abstract: According to a method of measuring a thickness, to measure a thickness d of a liquid crystal layer 11, a property of reflected light is utilized, in that the light returns maintaining the same polarizing plane as that of an entrance when a polarizing plane-maintaining condition is satisfied in which a difference in optical path lengths between an ordinary ray and an extraordinary ray of the reflected light is a sum of an integer multiple of the wavelength and a half-wavelength or an integer multiple, to find a wavelength at which the polarizing plane-maintaining condition is satisfied. A reasonable &Dgr;n·d is thereby found. This is performed for a plurality of wavelengths to find a relational expression of a wavelength and &Dgr;n·d. A known combination of a wavelength &lgr; and &Dgr;n is assigned to the relational expression to find d.