Optical: systems and elements – Mirror – Plural mirrors or reflecting surfaces
Reexamination Certificate
1998-03-12
2001-03-13
Spyrou, Cassandra (Department: 2872)
Optical: systems and elements
Mirror
Plural mirrors or reflecting surfaces
C362S347000, C349S067000
Reexamination Certificate
active
06199992
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a reflector, to a method of manufacturing the same, and to a display device using the reflector. More particularly, the present invention relates to a reflector having excellent directivity of reflected light which can provide increased intensity of the reflected light in a display device, such as a liquid crystal display device and so forth, and to a display device using the reflector.
2. Description of the Related Art
Display devices, such as liquid crystal display devices, include reflective display devices in which a reflecting surface is provided on the back of a display cell, semi-reflective display devices in which a semi-transmissive reflecting surface is provided on the back of the display cell and a backlight is further provided on the back thereof, and backlight-type display devices in which a backlight is provided behind the display cell. The above backlight is composed of a light guide element, a reflecting surface formed on the back of the light guide element, and a light source for providing light into the light guide element.
Hitherto, a flat mirror surface including a metal film, such as aluminum, deposited thereon, or a rough surface having the metal film deposited thereon has been employed as the reflecting surface.
When the reflecting surface is a flat mirror surface, light cannot be scattered at the reflecting surface, so that it is difficult to impart a sufficient display luminance to the display cell.
When the reflecting surface is a rough surface having the metal film deposited thereon, light can be scattered at the reflecting surface. However, the light scatters at the rough surface in random directions, while the effective viewing angle of a display cell, such as a liquid crystal cell, is limited to a fixed angle, so that the luminance of the reflected light cannot be effectively increased within the range of the effective viewing angle.
In order to allow the reflected light to have a directivity within the angle range in which the luminance of the reflected light increases, it is necessary to optically design the reflecting surface. In addition, it is necessary to form optically designed fine irregularities on the optical reflecting surface. In the conventional reflecting surface, however, it is difficult to form an optical surface having fine irregularities with high accuracy, and to manufacture the optical surface in large quantities.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a reflector which opically sets the shape of a reflecting surface so that the luminance of reflected light within a predetermined reflection angle can be increased, and which can set the angle range in which the luminance of the reflected light can be increased in relation to an effective viewing angle of a display cell, and to provide a display device using the reflector.
It is another object of the present invention to provide a method of manufacturing a reflector which can optically set the shape of the reflecting surface with fine irregularities, and which can form the irregularities by a simple process with high accuracy.
According to the present invention, the shape of the reflecting surface can be optically designed, and the reflecting surface can be easily manufactured by a process similar to that of manufacturing a hologram or the like.
That is, according to an aspect of the present invention, there is provided a reflector having a total-reflective or a semi-reflective reflecting surface, wherein the reflecting surface has a shape such that fine concave curves are arranged when viewed in cross section. The pitch of the concave curves is, for example, 50 &mgr;m or less.
By optically designing the shape of the fine concave curves, the luminance of reflected light can be increased within a predetermined angle range around a perpendicular line of the reflecting surface.
In addition, when a successive predetermined number of concave curves are taken as one set, it is preferable that different pitches of the concave curves are included in one set, and several units of concave curves are repeatedly formed, one set of concave curves being one unit. In this case, the width of one set of concave curves may be preferably 120 &mgr;n or less.
Thus, by changing the pitch of the concave curve regularly or at random within the range of 120 &mgr;m or more, for example, and by repeatedly form several sets of concave curves, the concave curves having the above width being one set, the light interference fringe phenomenon which presents fringe patterns or rainbow patterns due to the influence of the reflected light can be prevented.
The above concave surfaces being concave curves in cross section may be preferably formed in the shape of stripes, and the stripes of the concave surfaces may preferably extend in the shape of curves when the reflecting surface is viewed as a plane.
With such a construction, not only a directivity of the reflected light within the range in which the luminance of the reflected light increases can be optically set in a direction along the cross section perpendicular to the stripes (the X direction of FIGS.
6
A and
6
B), but also a distribution of the luminance in a direction perpendicular to the cross section (Y direction) can be set within a predetermined angle range around a perpendicular line of the reflecting surface, so that the range in which the luminance of the reflected light increases can be expanded.
In addition, the stripes may be preferably formed concentrically, for example, as shown in FIG.
6
B. In addition, according to the present invention, a number of three-dimensional concave surfaces, such as spherical concave surfaces may be formed adjacent to each other.
The reflecting surface when viewed in cross section may have any one of the following shapes.
When a line perpendicular to tangents to the lowermost portions of the concave curves is taken as a center line O
1
, the concave curves are circular curves extending symmetrically about the center line O
1
.
When a line perpendicular to tangents to the lowermost portions of the concave curves is taken as a center line O
1
, the concave curves on one side of the center line O
1
extend longer than those on the other side.
When a line perpendicular to tangents to the lowermost portions of the concave curves is taken as a center line O
1
, the concave curves are circular curves extending on one side with respect to the center line O
1
.
In this case, the side of the concave curves extending longer from the center line O
1
may be preferably directed downward with respect to a line of sight during usage.
When the reflecting surface having a shape such that the concave curves in cross section extend one side with respect to the center line O
1
is used with the concave curves extending one side directed downward, light from diagonally above can be effectively reflected to the front of the reflecting surface, so that the luminance of the reflected light can be increased in a direction of a user's line of sight.
In addition, if the reflector of the present invention is such that the concave surfaces being concave curves in cross section are formed in the shape of stripes in a direction intersecting the cross section, grooves traversing the stripes may be preferably formed at intervals in the concave surfaces extending in the shape of stripes. Further, the cross sections of the grooves may be preferably formed in a shape similar to that of the concave curves.
In a case in which the concave surfaces being concave curves in cross section extend in the shape of stripes, if the grooves traversing the stripes, i.e., the grooves along the concave curves are formed at intervals, all the directions of reflection of light can be concentrated onto the front of the reflecting surface. In this case, by optically designing the grooves to have a shape similar to that of the concave curves, the direction of reflection of light can be concentrated onto the front of the reflecti
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Spyrou Cassandra
Treas Jared
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