Abstract: Provided is a method for determining the ratio of a measurement object substance to a comparison object substance using a measuring reagent for the measurement object substance. The method makes it possible to easily determine, from an absorbance measured value, the ratio of the measurement object substance to the comparison object substance, using a single calibration curve (multiplexed calibration curve) which is not dependent on the concentration of the comparison object substance.

Abstract: There is provided a light diffusive plate and a light guide plate, in which the generation of deflection, a cause of defective imaging, can be prevented. On both surfaces and/or end surfaces of a light diffusive plate 1 made of synthetic resin, a moisture proof layer 2 made of a material having lower vapor permeability than that of the light diffusive plate 1 is formed to produce a light diffusive plate 3. On both surfaces and/or end surfaces of a light guide plate 1 made of synthetic resin, which has at least on end as a light incident surface and a surface almost orthogonal with it as a light emergent surface, a moisture proof layer 2 made of a material having lower vapor permeability than that of the light guide plate 1 is formed to produce a light guide plate 3.

Abstract: Because light diffusing plates constituting backlight units have high moisture absorbency, light diffusing plates cause deformation such as warp, swell and flexure and adversely affect other members such as liquid crystal cells to cause defective images. A backlight unit that does not generate defective images due to such deformation of light diffusing plate is provided. This backlight unit is a backlight unit 1 comprising light sources 13, a light diffusing plate 14 comprising a synthetic resin and disposed on the light sources, and one or more kinds of optical members 15 and 16 for backlight unit disposed on the light diffusing plate, wherein both surfaces of the light diffusing plate 14 shall have an arithmetical mean deviation (Ra) of 0.1 ?m or less according to JIS B0601:1994.