Abstract: An optical sheet constituted by a retardation film; and a transparent layer provided on one of opposite surfaces of the retardation film. The retardation film exhibits Nz=(nx=nz)/(nx=ny) in a range of from 0.1 to 0.4 and (nx−ny)d in a range of from 200 to 350 nm in which d is a thickness of the retardation film, nz is a refractive index in a direction of a Z axis expressing a direction of the thickness d of the retardation film, nx is a refractive index in a direction of an X axis expressing a direction of the retardation film in a plane perpendicular to the Z axis while the X axis also expresses a direction of the highest in-plane refractive index, and ny is a refractive index in a direction of a Y axis expressing a direction of the retardation film perpendicular both to the is Z axis and to the X axis. The transparent layer has a thickness not larger than 10 &mgr;m and exhibits refractive index anisotropy of nx∓ny>nz.

Abstract: An optical sheet is constituted by: a retardation film; and a transparent layer provided on one of opposite surfaces of the retardation film. The retardation film exhibits Nz=(nx−nz)/(nx−ny) in a range of from 0.4 to 0.6, both not inclusively, and (nx-ny)d in a range of from 200 to 350 nm when nx>ny in which d is the thickness of the retardation film, nz, nx and ny are a refractive index in a direction of the thickness d of the retardation film, a refractive index in a direction of the retardation film in the same plane as the direction of nx, and a refractive index in a direction of the retardation film in the same plane as the direction of nx, respectively. The transparent layer has a thickness not larger than 10 &mgr;m and exhibits refractive index anisotropy of nx≈ny>nz.

Abstract: An optical sheet constituted by a retardation film; and a transparent layer provided on one of opposite surfaces of the retardation film. The retardation film exhibits Nz=(nx−nz)/(nx−ny) in a range of from 0.6 to 0.9 and (nx−ny)d in a range of from 200 to 350 nm in which d is a thickness of the retardation film, nz is a refractive index in a direction of a Z axis expressing a direction of the thickness d of the retardation film, nx is a refractive index in a direction of an X axis expressing a direction of the retardation film in a plane perpendicular to the Z axis while the X axis also expresses a direction of the highest in-plane refractive index, and ny is a refractive index in a direction of a Y axis expressing a direction of the retardation film perpendicular both to the Z axis and to the X axis. The transparent layer has a thickness not larger than 10 &mgr;m and exhibits refractive index anisotropy of nx≈ny>nz.

Abstract: A light pipe includes a plate-like member having light output means formed in its upper surface so that light incident on an incidence side surface of the plate-like member is exited from the lower surface of the plate-like member through the light output means, an adhesive layer having a refractive index lower than that of the plate-like member, and (i) an anti-reflection layer made of a circularly polarizer and bonded to a lower surface of the plate-like member through the adhesive layer or (ii) a light-diffusing layer having a surface of fine prismatic structures and bonded to a lower surface of the plate-like member through the adhesive layer. A plane light source unit includes at least one light source disposed on one side surface of the light pipe. A reflection type liquid-crystal display device includes the plane light source unit and a liquid-crystal cell including a reflection layer disposed on the light output side of the plane light source unit.

Abstract: A reflective liquid crystal display (LCD) is constituted by a light pipe which emits incident light from an incident side from the other surface of its upper and lower surfaces through light emitting means formed on the one of them, a plane light source device with a light source arranged on one or more sides of the light pipe, and a liquid crystal display (LCD) panel having a reflective layer. The light emitting side of the plane light source device and the visual recognition side of the LCD panel are bonded to each other through an adhesive layer having a refractive index lower than that of the light pipe.

Abstract: A diffusing adhesive layer has a light-transmissible adhesive layer dispersively containing colorless light-transmissible particles so as to exhibit light diffusing characteristic. The light diffusing characteristic of the diffusing adhesive layer is not higher than 10% in terms of a light diffusion factor which is defined as 100×I30/I10 when I30 is the intensity of light transmitted in a direction inclined by 30 degrees relative to a direction of perpendicular transmission of perpendicularly incident light, and I10 is the intensity of light transmitted in a direction inclined by 10 degrees relative to the direction of perpendicular transmission of perpendicularly incident light. Another diffusing adhesive layer has a total light transmission factor of not lower than 85% and a direct transmission factor of not higher than 30%. In an optical member, one of the diffusing adhesive layers is provided on an optical material having at least a polarizing plate or a retarder plate.

Abstract: An alkaline secondary battery comprising a negative comprising cadmium, zinc or iron or an oxide or thereof or a hydrogen absorbing alloy, a positive electrode comprising a metal oxide or a metal hydroxide, and a separator, which are all impregnated with an electrolyte comprising an alkaline aqueous solution is disclosed, wherein the separator is made of a polyolefin fiber sheet which has a wicking rate of pure water of at least 10 mm per 2 minutes when one end of the sheet is dipped in pure water at 20.degree. C. and 60% RH. Since the separator is chemically stable and exhibits sufficient hydrophilic properties, the battery retains a high electrode utilization even at a high rate discharging and has a practically sufficient cycle life.