An object of the invention is to provide a reflector using a metal thin
film layer, particularly a reflector having higher reflectance than in
the prior art. Specifically, studies have been made to provide a
reflector which exhibits a superior reflection-increasing effect. As a
result, it has been found that if the thickness of a low refractive index
thin film layer (B) which comes in contact with a metal thin film layer
(A) is controlled so that it is within a range of 0.7 .lamda./8n.sub.L
1.3 .lamda./8n.sub.L, a reflector having an arrangement of metal layer
(A)/low refractive index thin film layer (B)/high refractive index thin
film layer (C) exhibits reflectance which is extremely superior than in
the prior art over a wide wavelength range. More specifically, it
exhibits higher reflectance than a pure silver single film does, and a
reflector superior in durability can be obtained. The lamp reflector,
reflector under the light-guiding plate of the invention uses the
above-mentioned reflector; therefore, if it is applied to each display
device, high brilliance and vivid image can be realized. Further, since
the liquid crystal display device of the invention uses the
above-mentioned reflector, a clear vivid image can be realized.