Illumination – Revolving
Reexamination Certificate
1999-06-28
2001-09-11
O'Shea, Sandra (Department: 2875)
Illumination
Revolving
C362S558000, C362S559000, C362S556000, C362S560000
Reexamination Certificate
active
06286970
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a spread illuminating apparatus used as front-face illuminating means for various reflection-type display units and so on, and more particularly to a spread illuminating apparatus used as illuminating means for a liquid-crystal display unit.
2. Background of Related Art
A liquid crystal display unit that operates with a low electric power consumption increases in demand as a display unit which is mainly used in association with a computer since it has the features such as a thin-type, light-weight, etc. Liquid crystal which is a structural element of the liquid crystal display unit requires illuminating means for illuminating an image, which is different from a light-emission type element such as a CRT, because the liquid crystal does not emit light by itself. In particular, in demand for thinning the apparatus in recent years, there is frequently used a spread illuminating apparatus of a thin-plate-like side light type (light-conductive plate type) as illuminating means for irradiating the liquid crystal display unit.
Hereinafter, the structure of a spread illuminating apparatus
41
of the side light type will be described referred to FIG.
15
.
Reference numeral
42
denotes a linear light source lamp such as a cold cathode fluorescent tube (CCFL) or a heat cathode fluorescent tube (HCFL) which is used as a light source of the spread illuminating apparatus. A transparent substrate
43
made of a material high in transmittance is shaped in a thin plate which is nearly rectangular in section. The light source lamp
42
is disposed at a given interval so as to be separated from and along one side end surface
44
thereof. For the purpose of illuminating the apparatus, the transparent substrate
43
may be shaped in a so-called wedge so as to be made gradually thinner as it is far from the one side end surface
44
along which the light source lamp
42
is disposed.
A lamp reflector
45
which is formed by evaporating silver or the like on a film is disposed on a portion, which is not opposite to the one side end surface
44
, of the peripheral surface of the light source lamp
42
. The provision of the lamp reflector
45
enables most of the light emitted from the light source lamp
42
to enter the interior of the transparent substrate
43
from the one side end surface
44
. In addition, in order to prevent the leakage of the light, a reflection material
47
formed of a reflection tape or the like is added to side surfaces except for the one side end surface
44
of the transparent substrate
43
(only the side end surface
46
which is an opposite surface of the one side end surface
44
is shown in FIG.
15
).
A light scattering pattern
49
(which will be described in detail later) is formed on a back surface
48
(lower side of
FIG. 15
) of the transparent substrate
43
in order to allow a light to be uniformly emitted from a screen of the spread illuminating apparatus unit without being influenced by a distance from the light source lamp
42
, and a reflector
50
is disposed so as to cover the entire surface of the back surface
48
on the lower portion of the light scattering pattern
49
. The reflector
50
allows a light which is supposed to be emitted from the back surface
48
of the transparent substrate
43
to be reflected thereby and to progress toward the front surface
51
of the transparent substrate
43
(toward an upper portion of FIG.
15
).
Further, a diffusing plate
52
is disposed in the spread illuminating apparatus
41
so as to cover the entire front surface
51
of the transparent substrate
43
. In order to avoid a phenomenon (a so-called dot image) that only the pattern of the light scattering pattern
49
is observed brightly because most of the light which progress in the transparent substrate
43
and is emitted from the front surface
51
is reflected at the light scattering pattern
49
, the diffusing plate
52
is disposed, thereby a light passed through the diffusing plate
52
is superimposed on each other (that is, the light is diffused) to make the density and the emission distribution of a light substantially uniform to realize the uniform emission of the light on the screen.
The light scattering pattern
49
shown in
FIG. 16
is formed in such a manner that the diameter of dots gradually increases from the one side end surfaces
44
, along which the light source lamp
42
is disposed, toward the side end surfaces
46
which is an opposite surface of the one side end surface
44
, for example, as disclosed in Japanese Patent Laid-open Publication No. Hei 5-134251. The light scattering pattern
49
is formed by coating a light diffusion-reflection material directly on the back surface
48
of the transparent substrate
43
by the screen printing system.
In this way, the light scattering pattern
49
allows the amount of light reflected thereby and emitted from the front surface
51
to change because the light scattering pattern
49
is formed by changing a rate of the light diffusion-reflection material per unit area depending on its location (hereinafter, the rate of predetermined material per unit area being called “area density”). That is, the light becomes higher in luminance as it is near the light source lamp
42
. Therefore, in order to realize the uniform spread light emission, the light scattering pattern
49
is formed in such a manner that the area density of the light scattering pattern
49
increases more as it is far from the light source lamp
42
with the result that the amount of light reflected on the front surface
51
side increases more as it is far from the light source lamp
42
. Therefore, taking the distance from the light source lamp
42
and the amount of light reflected by the light scattering pattern
49
into consideration, the light source lamp
42
is adapted to uniformly emit the light as a whole. The light scattering pattern
49
is indicated by oblique lines in
FIG. 16
for the facilitation of understanding although it is not of a section.
The above-described light scattering pattern
49
is structured to coat the light diffusion-reflection material on the back surface
48
of the transparent substrate
43
. However, since it is essential that the pattern
49
have a function of increasing the amount of reflected light, the pattern
49
may be designed in such a manner that a fine-concave/convex surface is formed directly on the back surface
48
of the transparent substrate
43
, and the light is diffused or reflected by the concave/convex surface, for example, as disclosed in Japanese Patent Laid-open Publication No. Hei 9-33923.
Subsequently, a description will be given of the structure of an illuminating apparatus different from the above-described spread illuminating apparatus
41
, which is particularly used as an auxiliary illuminating apparatus of the reflection type liquid crystal display device which is the illuminating means of the liquid crystal display device. Since the reflection type liquid crystal display device is structured in such a manner that the surrounding light is employed as illumination so that it can be irradiated on the screen when the surroundings are bright, no illuminating means is required inside of the device. However, in a case where the surroundings are relatively dark, since there occurs a drawback that it is difficult to observe an image, the auxiliary illuminating apparatus is required.
As an appropriate auxiliary illuminating means of the reflection type liquid crystal element of this type, there is disclosed, in Japanese Patent Application No. Hei 9-347648, a spread illuminating apparatus disposed on a front surface (screen side) of the reflection type liquid crystal element.
A transparent and spread illuminating apparatus
1
′ shown in
FIG. 17
is disposed so as to cover the observation face F of the reflection type liquid crystal element L thus structured in use, and its structure is that a linear light source lamp
4
is disposed so as to be close to one side end
Egawa Motoji
Suzuki Shingo
Minebea Co. Ltd.
O'Shea Sandra
Oliff & Berridg,e PLC
Zeade Bertrand
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