Lenticular lens, light-diffusing sheet, and projection screen

A light-diffusing sheet comprising:

• a lens element sheet containing a base film, a prism lens formed on one surface of the base film, and a lenticular lens formed on the other surface of the base film, and
• a support laminated to the lens element sheet,
• where parallel light entering the light-diffusing sheet from the prism lens side emerges from the support side, characterized in
• that the lenticular lens has multiple convex unit lenses disposed on the base film with their long sides parallel to each other,
• that the two edges of each unit lens on its section vertical to the longer direction are a pair of curves spreading outwardly from the upside of the cross section, situated on the side opposite to the base film, to the base of the cross section, situated on the base film side, and
• that a space between each two adjacent unit lenses is filled with a resin having a refractive index lower than that of the unit lenses, and
• wherein the angle θ between a tangent to the curves of each unit lens and a line parallel to the upside and base of the unit lens is acute, and the angle θ with any line parallel to the upside and base of the unit lens is in a range represented by the following inequality:
• 139(d/p)3−176(d/p)2+78(d/p)+74.4>θ>346(d/p)3−469(d/p)2+219(d/p)+45.0
• where d is the length of half of the distance between the two curves, and p is the pitch at which the unit lenses are disposed.

A projection screen comprising:

• a Fresnel lens, and
• a lenticular lens,
• the lenticular lens being formed on a base film and comprising multiple convex unit lenses disposed on the base film with their long sides parallel to each other,
• the two edges of each unit lens on its section vertical to the longer direction being a pair of curves spreading outwardly from the upside of the cross section, situated on the side opposite to the base film, to the base of the cross section, situated on the base film side,
• the angle θ between a tangent to the curves of each unit lens and a line parallel to the upside and base of the unit lens being acute,
• the angle θ with any line parallel to the upside and base of the unit lens being in a range represented by the following inequality:
• 139(d/p)3−176(d/p)2+78(d/p)+74.4>θ>346(d/p)3−469(d/p)2+219(d/p)+45.0
• where d is the length of half of the distance between the two curves, and p is the pitch at which the unit lenses are disposed.

A projection screen comprising:

• a Fresnel lens, and
• a light-diffusing sheet,
• the light-diffusing sheet comprising:
• a lens element sheet containing a base film, a prism lens formed on one surface of the base film, and a lenticular lens formed on the other surface of the base film, and
• a support laminated to the lens element sheet,
• where parallel light entering the light-diffusing sheet from the prism lens side emerges from the support side, characterized in
• that the lenticular lens has multiple convex unit lenses disposed on the base film with their long sides parallel to each other,
• that the two edges of each unit lens on its section vertical to the longer direction are a pair of curves spreading outwardly from the upside of the cross section, situated on the side opposite to the base film, to the base of the cross section, situated on the base film side, and
• that a space between each two adjacent unit lenses is filled with a resin having a refractive index lower than that of the unit lenses,
• wherein the angle θ between a tangent to the curves of each unit lens and a line parallel to the upside and base of the unit lens is acute, and the angle θ with any line parallel to the upside and base of the unit lens is in a range represented by the following inequality:
• 139(d/p)3−176(d/p)2+78(d/p)+74.4>θ>346(d/p)3−469(d/p)2+219(d/p)+45.0
• where d is the length of half of the distance between the two curves, and p is the pitch at which the unit lenses are disposed.