Optical: systems and elements – Diffusing of incident light
Reexamination Certificate
2002-04-18
2004-08-24
Juba, Jr., John (Department: 2872)
Optical: systems and elements
Diffusing of incident light
C359S627000, C349S113000
Reexamination Certificate
active
06781759
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a reflector, a production method thereof, a display element, and a display device, and more particularly, to a reflective display element and a reflective display device in which a non-emissive light modulating layer is employed.
BACKGROUND ART
A liquid crystal display, which is a typical example of a non-emissive display element, is categorized into a transmissive liquid crystal display in which a backlight is disposed at the back and a reflective liquid crystal display in which a reflector is disposed at the back to utilize external light for illumination. However, the reflective liquid crystal element is advantageous in that a liquid crystal can be driven at a low voltage of a few volts, and thus operation is realized with extremely low power consumption. In the case of the reflective liquid crystal element, a diffuse reflector made of aluminum or silver is disposed behind the liquid crystal layer, while in the case of a black-and-white reflective liquid crystal incorporated into, for example, a watch, configuration is such that a diffuse reflector having a polarizer is attached to the outside of the glass.
In Japanese Unexamined Patent Publication No. 4-243226, in order to fabricate a diffuse reflector whose shape can be controlled with good reproducibility on the inner surface of the glass, a diffuse reflecting film is fabricated as follows. As shown in
FIG. 19
, a resist film
52
is coated on a glass substrate
51
and is exposed to light exposure through a photomask
53
, and after a plurality of protrusions
54
spaced apart from one another are formed, the edges of each protrusion are rounded by performing a heat treatment, and then over the structure, a metal reflecting film
56
is formed.
In Japanese Unexamined Patent Publication No. 6-27481, in order to prevent interference colors from being generated by flat portions that are not patterned as disclosed in the above-mentioned Japanese Unexamined Patent Publication No. 4-243226, protrusions
60
are coated with a polymeric resin
61
to form smooth and continuous depressions and protrusions as shown in FIG.
20
.
Sugiura et al. propose a window type scattering characteristic such that the intensity of reflected light is constant within a certain angle range (see solid line
62
in
FIG. 21
) as a scattering characteristic that realizes higher brightness in a wide viewing angle range, and as a shape capable of realizing such a scattering characteristic, Sugiura et al. propose a method whereby a continuous curved surface
65
is formed such that convex-down quadratic functions
63
and convex-up quadratic functions
64
are joined together as shown in
FIG. 22
(see, for example, AM-LCD '95, Digest of Technical Papers, pages 153-156, Norio Sugiura and Tatuso Uchida, August 1995).
However, with the prior art reflectors in which a reflecting film is provided on the protrusions spaced apart from one another or is provided on the continuous curved surface formed by leveling off the protrusions spaced apart from one another with a resin (as shown in FIG.
20
), the reflected light intensity is highest in the directions of specular reflection and the exit angle dependency is high. This creates problems for the reflection characteristics, for example, display may appear metallic. Although the window type scattering characteristic may make a preferable countermeasure for these problems, the continuous curved surface defined by quadratic functions (those shown in
FIG. 22
) proposed by Sugiura et al. are defined two-dimensionally as is understood from the equation, and the scattering direction is limited to one direction. Therefore, scattering does not occur with respect to light entering from a direction orthogonal to this direction, and thus the continuous curved surface offers no practical use. Consequently, at the present, a window type scattering characteristic with a small amount of direction dependency is yet to be realized, and a three-dimensional shape for a reflector having depressions and protrusions that show such characteristics is desired.
DISCLOSURE OF THE INVENTION
In view of the foregoing problems, it is one of the objects of the present invention to realize a window type scattering characteristic with a small amount of direction dependency by improving a reflector and to provide a display element and a display device in which bright displays with a wide range of viewing angles as well as paper white displays free from sense of metallicity are possible.
It is another object of the present invention to provide a method of easily producing the aforementioned reflector, display element, and display device.
In order to solve the foregoing problems, in a first reflector of the present invention comprising a reflecting film formed on a surface having depressions and protrusions, each of the depressions and protrusions has a vertex and is composed of a curved surface formed so as to be convex up or convex down and a surrounding portion including a valley or a ridge surrounding the curved surface with an inflection point of the curved surface serving as a boundary between the curved surface and the surrounding portion, and when the curved surface is convex up, the inflection point is on the valley side of the midpoint between the vertex and the valley, whereas when the curved surface is convex down, the inflection point is on the ridge side of the midpoint between the vertex and the ridge.
Preferably, when cross-sectional shapes of the curved surfaces are made similar by defining the cross-sectional shapes by z=&agr;x
a/2
+&bgr;, where z is the thickness direction, x is the horizontal direction, and &agr; and &bgr; are constants, the average value of “a” for the protrusions is fixed to be greater than 2 and equal to or less than 4.
By using a reflector having such a configuration, it is possible to realize a window type scattering characteristic with a small amount of direction dependency, thereby enabling the provision of bright displays with a wide viewing angle
In addition, it is preferable that each curved surface of such a reflector have a width two or more times the width of the surrounding portion.
Furthermore, by making the average value of “a” greater than 2 and equal to or less than 3 and the intensity of reflected light that is reflected by the reflector such that light in a direction of specular reflection of incident light has a higher intensity than diffusely reflected light in a direction of scattering of incident light at a specified reflection angle, it is possible to realize an unprecedented reflection characteristic such that the viewing angle direction is even brighter than the specular reflection direction.
Additionally, when adjacent convex up or convex down curved surfaces are close to one another and there are substantially no surrounding portions, specular reflected light is suppressed more, and thus easily viewable displays can be obtained. It is especially easy to produce a shape such that the shape having depressions and protrusions comprises only either convex up or convex down and the sign of the slope of inclined surfaces of adjacent protrusions is reversed at every boundary between the depressions or protrusions
In a second reflector of the present invention having a reflecting film formed on a surface with a plurality of depressions and protrusions made up of a continuous curved surface, when cross-sectional shapes having vertexes of the depressions or the protrusions as origins are made similar by defining the cross-sectional shapes by z=&agr;x
a/2
+&bgr;, where z is the thickness direction, x is the horizontal direction, and &agr; and &bgr; are constants, the average value of “a” for the plurality of depressions and protrusions is fixed to be greater than 2.5 and less than 3.5.
In a display element and a display device incorporating a reflector such as the above-described second reflector, it is possible to provide bright displays with a wide viewing angle at low power consumption, as is the case with t
Kawaguri Mariko
Nishiyama Seiji
Wakita Naohide
Jr. John Juba
Matsushita Electric - Industrial Co., Ltd.
Parkhurst & Wendel L.L.P.
LandOfFree
Reflector, production method thereof, display element, and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Reflector, production method thereof, display element, and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Reflector, production method thereof, display element, and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3352274