Light adjusting sheet for a planar lighting device and a planar lighting device and a liquid crystal display using the sheet

DETAILED DESCRIPTION Accordingly, it is an object of the present invention to provide a light adjusting sheet for a planar lighting device in which the emanated light distribution can be concentrated in the forward direction of the screen, and no Moire fringes occur.
It is another object of the present invention to provide a light adjusting sheet for a planar lighting device which gives greater luminance in the forward direction compared with the case when no light adjusting sheet is used, gives a wider sight angle than the conventional light adjusting sheet, and assures prevention of optically tight contact with the light guiding plate.
It is a further object of the present invention to provide a light adjusting sheet for a planar lighting device which gives a suitable span in the direction of the user's sight and an improved brighter screen.
It is still a further object of the present invention to provide a light adjusting sheet for a planar lighting device with reduced reflection at the front surface thereof, with no interference fringes, and also with the irregular reflection layer made invisible.
It is yet another object of the present invention to provide a planar lighting device of an edge-light type which can illuminate a screen of a display brightly and uniformly.
Further, it is yet further an object of the present invention to provide a liquid crystal display in which the screen is bright and easily seen.
According to one aspect of the present invention, a light adjusting sheet has one surface provided with a plurality of convex ridges or regions each having a cross section of a convex arc and a plurality of concave ridges or regions each having a cross section of a concave arc alternately arranged approximately parallel to each other, and the other surface which is a non optical-flat surface.
Each of the convex regions and concave regions are formed by two flat surfaces.
Throughout the specification, the term "sheet" includes not only a sheet in the strict sense limited by the thickness, but also a thinner one which is usually called "film"