Illumination – Revolving
Reexamination Certificate
1999-04-19
2001-03-06
Cariaso, Alan (Department: 2875)
Illumination
Revolving
C362S330000, C349S063000, C349S065000
Reexamination Certificate
active
06196692
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a light conductive plate with which a reflection type liquid-crystal display which is bright and easy to view can be fabricated. The present invention further relates to a surface light source device which employs the light conductive plate and in which light can be utilized highly effectively.
BACKGROUND OF THE INVENTION
There is a desire for an illuminator which enables a reflection type liquid-crystal display to be read in the dark or the like. The present inventors attempted to apply a backlight for use in transmission type liquid-crystal displays to a front light system in which the backlight is disposed on the viewing side of a liquid-crystal cell. This backlight has a light conductive plate in which incident light from a side edge is emitted through a light-emitting means from one of the upper and lower surfaces. In the front light system, the displayed information is viewed through the light conductive plate.
However, the backlights employing conventional light conductive plates have been difficult to put to practical use because they pose problems that the display is insufficient in contrast in an illuminated state, has insufficient brightness in an unilluminated state, and has display disturbance, etc. For example, a liquid-crystal display having a light conductive plate employing diffusing dots or fine roughness as a light-emitting means has the following problems. The display is insufficient in contrast when viewed in an illustrated state. When viewed in an unilluminated state with external light, e.g., indoor lighting, the display is insufficient in contrast and has insufficient display brightness. In addition, the displayed images on the unilluminated display, which are viewed through the light conductive plate, are considerably disturbed and have poor clearness.
On the other hand, a light conductive plate has been proposed which employs as a light-emitting means a staircase-like prismatic structure having inclined faces with an angle of inclination of 45 degrees and flat faces with an angle of inclination of 0 degree (see JP-A-62-73206; the term “JP-A” as used herein means an “unexamined published Japanese patent application”). Even a liquid-crystal display having this light conductive plate has a problem that it is insufficient in contrast and display brightness when viewed in an illuminated state.
The above liquid-crystal display further had the following problem. Part of incident light is reflected by the lower surface of the light conductive plate without entering the liquid-crystal cell, etc., and leaks through the upper surface thereof. When this liquid-crystal display is viewed from the upper side, the resultant leakage light is superposed on displayed images, regardless of whether the display is in an illuminated state or not, to cause white blurring and reduced contrast, resulting in impaired perceptibility.
SUMMARY OF THE INVENTION
One object of the present invention is to provide a reflection type liquid-crystal display which is excellent in contrast when viewed with or without illumination and also in display brightness and in which displayed images viewed through a light conductive plate are less apt to be disturbed, i.e., excellent in clearness, and are less apt to have a decrease in perceptibility caused by moire phenomenon.
Another object of the present invention is to provide a light conductive plate and a surface light source device with each of which the liquid-crystal display can be fabricated.
The present invention provides a light conductive plate having, formed on the upper surface thereof, a light-emitting means which serves to deflect incident light from an incidence-side edge of the plate to emit the light through the lower surface of the plate and further having, at least on the lower surface thereof, an antireflection layer which enables incident light from the lower surface of the plate to pass through the upper surface of the plate.
The present invention further provides: a surface light source device comprising the light conductive plate described above and a light source disposed by the incidence-side edge thereof.
The present invention also provides a reflection type liquid-crystal display comprising the surface light source device described above and, disposed on the lower side thereof, a liquid-crystal cell having a reflecting layer.
REFERENCES:
patent: 5341231 (1994-08-01), Yamamoto et al.
patent: 0 787 942 (1997-08-01), None
patent: 0 879 991 (1998-11-01), None
patent: 261684 (1995-11-01), None
patent: 279206 (1996-06-01), None
patent: 346635 (1998-12-01), None
Patent Abstracts of Japan, vol. 11, No. 274 (P-612), Sep. 5, 1987 & JP 62 073206 A (Hitachi) Apr. 3, 1987 *Abstract.
Abe Hideo
Umemoto Seiji
Yano Shuji
Cariaso Alan
Nitto Denko Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
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