Kuraray Co., Ltd.

Toshitaka Kunisawa

Toshiyuki Yoshikawa

Osamu Shinji

Kouzo Yasuda

Kozo Yasuda

A lightguide which guides light from at least one side end plane and includes a plurality of approximately trapezoidal protrusions whose apex edge in the cross section perpendicular to the axis of a linear light source has a partially straight section. The approximately trapezoidal protrusions are arranged on the rear surface of the lightguide, opposing a light emitting surface. The approximately trapezoidal protrusions are arranged in a pattern of specks, solid lines, or broken lines. The pattern has a low area density in a region neighboring the at least one side end plane and at a high area density in a region removed from the at least one side end plane such that the luminance distribution of the light emitted from the light emitting surface is approximately uniform. Preferably, the approximately trapezoidal protrusions have, in the same cross section, two rounded corners, and the roughness of the surface that includes the apex edge of the protrusions, the roughness of the rear surface excluding the protrusions, is less than 0.2 &mgr;m, the ratio of the height H to the width W of the approximately trapezoidal protrusions in the same cross-section be 0.1&lE;H/W&lE;0.6, and the width W is 20 &mgr;m&lE;W&lE;200 &mgr;m.

Lightguide

A transparent lightguide (,) which guide light at least from one side end plane is characterized in that a large number of speckled, solid-line shaped or broken-line shaped protruding patterns whose cross-sectional width W (&mgr;m) at a cross section perpendicular to the axis of a linear light source is 10&lE;W&lE;200 are arranged on a light emitting surface at a low density in a region close to the linear light source and at a high density in a region far from the linear light source so as to make the luminance distribution of the light emitted from the light emitting surface approximately uniform. Here, the cross section of the protruding pattern is preferable to be approximately trapezoidal while having a straight part partially and the ratio H/W to be 0.2&lE;H/W&lE;1.0, where W and H denote cross-sectional width and height of the protruding pattern, respectively, or the cross section of the protruding pattern is preferable to be approximately circular-arc and the ratio H/W to be 0.2&lE;H/W&lE;0.5, where W and H denote cross-sectional width and height of the protruding pattern, respectively.

Lightguide having trapezoidally-shaped main body with a level surface at an angle to a rear surface

The present invention includes the steps of forming a stamper with a fine and delicate relief pattern formed thereon by forming a photo resist layer on a flat substrate, exposing the photo resist, developing the exposed photo resist, metallizing and electroforming the surface of the photo resist, and of injection molding the light-transmitting plate using said stamper.

Growing community of inventors

Niigata, Japan

Toshitaka Kunisawa