Surface illumination device suitable for a backlit display
US5797668A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 2, 1997 |
| Grant date | Aug 25, 1998 |
| Priority date | — |
| Expiry date | Apr 2, 2017 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02B6/0051
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A lens film provided in front of a light guide plate of a surface illuminant device comprises a base film, and a plurality of triangular parallel prisms formed in a two-dimensional arrangement on one surface of the base film integrally with the latter to form an exit surface. Each prism has a cross section of the shape of a isosceles triangle. The shape of the triangular prisms meets conditions represented by: ##EQU1## 0.5.ltoreq.R.ltoreq.1.0 where .theta.1 is a peak exit angle at which a direction, in which most part of light leaving an exit surface of a light guide plate toward the lens film travels, is inclined to a normal to an entrance surface of the lens film, .theta..sub.2 is an apex angle of the triangular prisms, and n is refractive index of the lens film. The lens film deflects incoming light so that most part of the light leaving the lens film travels in a direction substantially parallel to a normal to its imaginary exit surface, and serves to increase the head-on luminance.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.