Keiwa Inc.

Yoshitada Namikawa

Yuki Matsuno

Kenichi Harada

Tadayoshi Fukuda

Hirohisa Dejima

A backlight unit () includes a light guide sheet () and a light diffusion sheet () provided on the surface of the light guide sheet (). Assuming that the coefficient of static friction between the light guide sheet () and the light diffusion sheet () measured at a temperature of 23&#xb0; C. and a humidity of 50% in accordance with JIS K 7125 is Y, and the difference in coefficient of linear expansion between the light guide sheet () and the light diffusion sheet () measured in accordance with JIS K 7197 is X, the following relational expression (1) is satisfied.[Math. 1]&#x2264;1.00&#xd7;10&#x2212;3.43&#xd7;10+2.35&#x2003;&#x2003;(1).

Backlight unit and liquid crystal display device

An optical sheet for a backlight unit for guiding toward a front face side rays of light emitted by an LED light source. The optical sheet includes one or more resin layers. Ultrafine grooves oriented in specific directions are provided on a front face side or a back face side of at least one resin layer of the one or more resin layers. An average number of the ultrafine grooves per unit length in a direction perpendicular to an average orientation of the ultrafine grooves is preferably no less than 10/mm and no greater than 10,000/mm. A face of the at least one resin layer provided with the ultrafine grooves preferably has an arithmetic average roughness (Ra) in a direction perpendicular to an orientation of the ultrafine grooves being no less than 0.01 &#x3bc;m and no greater than 5 &#x3bc;m. Ultrafine grooves preferably constitute a diffraction grating.

Optical sheet for backlight unit and backlight unit

A backlight unit satisfies the relationship given by the following expression: S&#x3c;2(A&#x2212;&#x221a;3T), where A (mm) represents the length along which the light shielding member covers the light diffusion sheet before shrinkage, T (mm) represents the thickness of the prism sheet, and S (mm) represents the amount of shrinkage of an end on the frame side of the light diffusion sheet in the planar direction of the light diffusion sheet. The backlight unit also satisfies the relationship given by the following expression: E&#x3c;D, where D (mm) represents the distance between the end on the frame side of the light diffusion sheet before expansion and a frame and E (mm) represents the amount of expansion of the end on the frame side of the light diffusion sheet in the planar direction of the light diffusion sheet.

Provided is a prism sheet for a backlight unit capable of attaining desired luminance in the front direction, and securing a sufficient viewing angle in the direction perpendicular to the orientation direction of the prism array. The prism sheet comprises one or more resin layers, an outermost resin layer of the one or more resin layers comprising a prism array, wherein on a surface of at least one of the one or more resin layers, micro linear grooves are formed to be parallel to, or to intersect at an acute angle with, an orientation direction of the prism array. An average number of existing micro linear grooves per unit length in a direction perpendicular to an average orientation direction of the micro linear grooves is preferably no less than 30/mm and no greater than 10,000/mm. The micro linear grooves are preferably irregular in length, width or pitch.

Prism sheet for backlight unit and backlight unit for liquid crystal display device

An optical sheet for a liquid crystal display device has functions of condensing rays of light with respect to a specific direction in a plane of the optical sheet, and diffusing rays of light with respect to a direction perpendicular to the specific direction. A backlight unit for a liquid crystal display device includes: a light guide film for guiding rays of light incident on an end face of the light guide film toward a front face side; at least one LED light source disposed along the end face of the light guide film; the optical sheet disposed on the front face side; and a prism sheet disposed on a front face of the optical sheet, with the specific direction being parallel to a direction of rays of light emitted by the at least one LED light source and perpendicular to a direction of prism rows of the prism sheet.

Optical sheet for liquid crystal display device, and backlight unit for liquid crystal display device

An optical sheet for a liquid crystal display device includes a plurality of protruding portions provided scatteredly on a back face, in which the protruding portions each have a flattened semi-spherical shape or a flattened conical shape with a rounded apex. The protruding portions may each have a half spheroidal shape. An occupancy area ratio of the plurality of protruding portions may be no less than 2% and no greater than 80%. An average diameter of the protruding portions may be no less than 5 &#x3bc;m and no greater than 60 &#x3bc;m, and an average height of the protruding portions may be no less than 0.5 &#x3bc;m. A diffraction grating shape with multiple rows that are oriented in a single direction on the back face in a region where the plurality of protruding portions are absent.

Optical sheet for liquid crystal display device, backlight unit for liquid crystal display device and production method of optical sheet for liquid crystal display device

An optical sheet includes: a transparent substrate sheet; and a sticking preventive portion provided on the back face of the transparent substrate sheet. The sticking preventive portion includes a plurality of printed dots. The average diameter of the printed dots is preferably no less than 1 &#x3bc;m and no greater than 200 &#x3bc;m. The ratio of the average height to the average diameter of the printed dots is preferably no less than 1/100 and no greater than 1. The printed dot preferably has a hemisphere-like shape having a height less than a diameter. The arrangement density of the printed dots on the back face of the substrate sheet is preferably no less than 10 dots/mmand no greater than 2,500 dots/mm. A principal component of the printed dots is preferably is preferably an acrylic resin, a urethane resin or an acrylic urethane resin.

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Tokyo, Japan

Yoshitada Namikawa