Illumination – Revolving
Reexamination Certificate
1998-07-06
2001-06-19
Husar, Stephen (Department: 2875)
Illumination
Revolving
C362S026000, C362S027000, C349S063000, C349S065000
Reexamination Certificate
active
06247826
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin sheet-form illumination device for illuminating objects to be illuminated such as images printed on paper, liquid crystal displays, or solid objects, and to a bulletin board device or the like employing an illumination device according to the present invention.
2. Description of the Related Art
As in Early Japanese Patent Publication No. H.6-324331, in a conventional sheet illumination device arranged at the front face of for example a liquid crystal display, the light-guide plate constituting the illumination device consists in a flat plate of high rigidity.
However, since in the conventional sheet illumination devices, the light guide plate was a flat plate of high rigidity, and as the conventional liquid crystal display devices etc. using flat rigid bodies made of for example glass were mostly employed for illumination of planar articles of high rigidity, when they were employed for illumination of objects having curved surfaces or flexibility, irregular spaces were produced between the illumination device and the illuminated object, making uniform illumination difficult to achieve and impairing flexibility of the illuminated object: thus they were sometimes unsuitable for their purpose.
SUMMARY OF THE INVENTION
An object of the present invention is to solve such problems and provide an illumination device wherein the degrees of freedom of shape of the object to be illuminated are not reduced and whose adaptability in terms of design is high, and to a bulletin board device employing this illumination device, by making the light guide plate a curved surface or by conferring flexibility on the light guide plate.
In order to solve the aforementioned problem an illumination device according to the present invention.
(1) in an illumination device arranged at the front face of an object to be illuminated, comprises: a light guide plate which has optical diffusion shapes on at least one plate face of a transparent plate having a curved surface: and a light source arranged adjacent an end face of this light guide plate.
(2) In a cross-section produced by a plane containing part of said light source of said light guide plate, said light guide plate having an approximately fixed thickness of t, if &thgr; is the angle with respect to the tangential plane of this plate surface of said light guide plate at said end face of incident light from said end face adjacent which said light source is arranged, n1 is the refractive index of said light guide plate, n2 is the refractive Index of the medium contacting this plate face of said light guide plate, and r is the radius of curvature on the side of said light guide plate of smallest plate face, the condition:
t/r
≦(
n
1
2)×cos &thgr;−1
is satisfied.
(3) The end face at which at least said light source is arranged adjacently is approximately perpendicular with respect to the tangential plane of the plate face of said light guide plate, said light guide plate has an approximately fixed thickness of t, and, in a cross-section based on the plane containing part of said light source of said light guide plate, if the refractive index of said light guide plate is n1, the refractive index of the medium containing the plate face of said light guide plate is n2, and the refractive index of the medium contacting said end face where the light source of said light guide plate is arranged is n3 and the radius of curvature of the smaller plate face of said light guide plate is r, the condition
t/r
≦(
n
1
2
−n
3
2
)
½
2−1
is satisfied.
(4) An illumination device arranged at the front face of an object to be illuminated comprises; a light guide plate formed with optical diffusion shapes on at least one plate face of a transparent plate formed of flexible transparent material; and a light source arranged adjacent an end face of this light guide plate.
(5) A transparent film is arranged adjacent at least one plate face of said light guide plate, with interposition of an air layer.
(6) Said optical diffusion shapes are projecting shapes provided on the side of said light guide plate nearest the object to be illuminated.
(7) Said projecting shapes are constituted of side faces approximately perpendicular with respect to the tangential plane of the plate face of said light guide plate and bottom faces approximately parallel thereto.
(8) Said projecting shapes are cylindrical pillar shapes.
(9) Said optical diffusion shapes are convex shapes provided on the face of said light guide plate on the opposite side with respect to the object to be illuminated.
(10) Said optical diffusion shapes are concave shapes provided on the face of said light guide plate on the opposite side with respect to the object to be illuminated. Also a bulletin board device according to the present invention employs an illumination device according to the present invention.
Also a timepiece according to the present invention employs an illumination device according to the present invention.
Also a portable illumination device according to the present invention employs an illumination device according to the present invention.
Also a display device according to the present invention employs an illumination device according to the present invention.
Also electronic equipment according to the present invention employs a display device according to the present invention.
Also a mobile telephone device according to the present invention employs a display device according to the present invention.
REFERENCES:
patent: 2071777 (1937-02-01), Bloem
patent: 2646637 (1953-07-01), Neirenberg et al.
patent: 4697365 (1987-10-01), Mossbrugger et al.
patent: 4779166 (1988-10-01), Tanaka et al.
patent: 5153590 (1992-10-01), Charlier
patent: 5341231 (1994-08-01), Yamamoto et al.
patent: 5394255 (1995-02-01), Yokota et al.
patent: 5396406 (1995-03-01), Ketchpel
patent: 5477423 (1995-12-01), Fredriksz et al.
patent: 5815225 (1998-09-01), Nelson
patent: 6-324331 (1994-11-01), None
Funamoto Tatsuaki
Yokoyama Osamu
Husar Stephen
Oliff & Berridg,e PLC
Seiko Epson Corporation
Ward John Anthony
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