Optical sheet, backlight and liquid crystal display apparatus
View Patent ↗An optical sheet has a large number of cylindrical lens elements provided successively on one of principal faces thereof. The cylindrical lens elements have a hyperboloidal face or a paraboloidal face and have a finite focal distance on the emission side of illumination light. Where a Z axis is taken in parallel to a normal line direction to the optical sheet and an X axis is taken in a direction of the row of the cylindrical lens elements, a cross sectional shape of the cylindrical lens elements satisfies Z=X 2 /(R+√{square root over ( )}(R 2 −(1+K)X 2 )) (where R is the radius of curvature of a distal end vertex, and K is a conic constant).
1. An optical sheet comprising cylindrical lens elements which have a hyperboloidal face or a paraboloidal face and are provided successively in a row on one of principal faces of said optical sheet,
wherein a Z axis is taken in parallel to a normal line direction to said optical sheet and an X axis is taken in a direction of the row of said cylindrical lens elements, and wherein a cross sectional shape of said cylindrical lenses satisfies the following expression:
Z=X 2 /( R +√{square root over ( )}( R 2 −(1 +K ) X 2 ))
where R is a radius of curvature of a distal end vertex, and K is a conic constant, and
wherein the radius R of curvature, the conic constant K and a configuration unit width D satisfy the following numerical ranges:
0<R<D
−4 <K≦ 1.
2. The optical sheet according to claim 1 , wherein the radius R of curvature and the conic constant K satisfy the following numerical ranges:
0 <R<D/ 2
−3 <K≦ 1.
3. The optical sheet according to claim 1 , wherein the radius R of curvature and the conic constant K satisfy the following numerical ranges:
0 <R< 2 D/ 5
−3 <K≦ 1.
4. A backlight comprising:
a light source for emitting illumination light; and
an optical sheet for raising a directivity of a illumination light emitted from said light source;
said optical sheet has, provided on one of principal faces thereof, cylindrical lens elements which have a hyperboloidal face or a paraboloidal face and are provided successively in a row;
where a Z axis is taken in parallel to a normal line direction to said optical sheet and an X axis is taken in a direction of the row of said cylindrical lens elements, a cross sectional shape of said cylindrical lenses satisfies the following expression:
Z=X 2 /( R+ √{square root over ( )}( R 2 −(1 +K ) X 2 ))
where R is the radius of curvature of a distal end vertex, and K is a conic constant, and
wherein the radius R of curvature, the conic constant K and a configuration unit width D satisfy the following numerical ranges:
0<R<D
−4 <K≦ 1.
5. A liquid crystal display apparatus, comprising:
a light source for emitting illumination light;
an optical sheet for raising the directivity of a illumination light emitted from said backlight; and
a liquid crystal panel for displaying an image based on the illumination light emitted from said optical sheet;
said optical sheet has, provided on one of principal faces thereof, cylindrical lens elements which have a hyperboloidal face or a paraboloidal face and are provided successively in a row;
where a Z axis is taken in parallel to a normal line direction to said optical sheet and an X axis is taken in a direction of the row of said cylindrical lens elements, a cross sectional shape of said cylindrical lenses satisfies the following expression:
Z=X 2 /( R+ √{square root over ( )}( R 2 −(1 +K ) X 2 ))
where R is the radius of curvature of a distal end vertex, and K is a conic constant, and
wherein the radius R of curvature, the conic constant K and a configuration unit width D satisfy the following numerical ranges:
0<R<D
−4 <K≦ 1.