Lens sheet and method of manufacturing the same

Abstract

In a lens sheet, a lens portion () made of activation energy curing resin such as ultraviolet curing resin has a plurality of lens units, the lens portion () is disposed on at least one side of a transparent substrate () such as plastic sheet, a relaxation layer () is disposed between the transparent substrate () and the lens portion (), and the thickness of the relaxation layer () is within a range of 1% to 30% of the height (H) of the lens units. The relaxation layer () is made of activation energy curing resin and formed integrally with the lens portion (). The refractive index of the transparent substrate () is lower than that of the lens portion (). The lens units are elongated prisms each having a substantially triangular cross section. The thickness of the relaxation layer is within a range of 1 μm to 10 μm, for example. The prisms have the vertical angle of 50° to 75° and are arranged with a pitch of 10 μm to 150 μm. The lens sheet having the relaxation layer () is obtained by providing activation energy curing composition to an area between a lens portion transferring pattern surface of a lens forming mold and one side of the transparent substrate to form a composition layer between the lens forming mold and the transparent substrate, and making the thickness of the composition layer uniform with use of a nip roll disposed so as to confront the other side of said transparent substrate while nip pressure of the nip roll is regulated by pressure regulating means. Due to the relaxation layer (), the deformation of the surface of the lens portion caused by polymerization shrinkage of the activation energy curing composition is suppressed so as to prevent occurrence of the optical defect in the lens sheet such as spot pattern, glare, etc.