Liquid crystal cells – elements and systems – Particular structure – Particular illumination
Reexamination Certificate
2000-09-19
2003-12-23
Dudek, James (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Particular illumination
Reexamination Certificate
active
06667782
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a light guide apparatus, a backlight apparatus and a liquid crystal display (LCD) apparatus using the backlight apparatus.
2. Description of the Related Art
A backlight apparatus has been used as a light source of an LCD apparatus. FIG.
1
(A) shows an LCD apparatus using a conventional backlight apparatus. The conventional backlight apparatus includes a fluorescent lamp
1
generating white light, a reflecting cover
2
mounted to surround a top side, a bottom side and a rear side of the fluorescent lamp
1
, a wedge-type light guide
3
, a light scattering layer
4
attached on the bottom surface of the light guide
3
, a metallic reflector
5
placed below the light guide
3
, and light-shaping films
6
and
7
placed above the light guide
3
. A prism sheet, which refracts the incidence light directed from an oblique direction toward a vertical direction of the prism sheet, is frequently used as the light-shaping films
6
and
7
. The light scattering layer
4
is actually a dotted pattern printed on the bottom surface of the light guide
3
.
Each of the dots diffuses the incidence light upwardly with a large angle distribution, as shown in a right side portion of the light scattering layer
4
in FIG.
1
. By controlling the density of the dots over the bottom surface of the light guide
3
, the backlight apparatus can uniformly pass the light through from the top surface of the light guide
3
. The emitted light from the top surface of the light guide
3
is diffused with a large angle distribution. For some applications such as an LCD apparatus for notebook personal computers, this angle distribution of the emitted light is so large that the efficiency of usage of the light from the light source, or the fluorescent lamp
1
is not high. Therefore, one or more light-shaping sheets are used to obtain the appropriate angle distribution. The metallic reflector
5
serves as a light recirculator, which can reflect the light leaking out from the bottom light scattering layer
4
back into the light guide
3
, for light recycling.
The light emitted by the backlight apparatus is directed to an LCD panel
10
through a polarizer
8
. A polarizer
9
also is placed above the LCD panel
10
. The LCD panel
10
includes an upper glass substrate
11
and a lower glass substrate
12
, and peripheral edges of both the glass substrates
11
and
12
are sealed by a sealing area
13
. A color filter which includes red, green and blue color filter segments, and a common electrode, not shown in FIG.
1
(A), are formed on the inner surface of the upper glass substrate
11
to realize the color LCD apparatus. One pixel is constituted by three sub-pixels (i.e., the R, G and B sub-pixels). The liquid crystal material, such as a 90-degrees twisted nematic (TN) liquid crystal material is enclosed within the space between the glass substrates
11
and
12
.
A first problem of the conventional backlight apparatus is that it is very difficult to obtain the light emitted with an angle spread less than 10 degrees FWHM (Full Width at Half Maximum), as shown in FIG.
1
(B).
Another problem of the conventional backlight apparatus is that the backlight apparatus requires many components, some of which are not easily fabricated, so that the fabrication cost becomes high.
A third problem of the conventional backlight apparatus is that since the light from the fluoresecent lamp
1
passes through many components, the intensity of the light is largely attenuated while passing through the components.
SUMMARY OF THE INVENTION
In view of the foregoing and other problems, disadvantages, and drawbacks of the conventional methods and structures, an object of the present invention is to provide a light guide and a backlight apparatus which emits light with an angle spread less than 10 degrees FWHM.
It is another object of the present invention to provide a light guide and a backlight apparatus with reduced fabrication cost.
It is yet another object of the present invention to provide a light guide and a backlight apparatus which improves the efficiency of usage of the light from the light source.
It is still another object of the present invention to provide an LCD apparatus using the light guide apparatus and the backlight apparatus mentioned above.
A backlight apparatus in accordance with a first aspect of the present invention includes a wedge-type light guide of a refractive index n
1
, having a top surface, a bottom surface and a side surface, a light source for directing light to the side surface of the wedge-type light guide, a first light transmission layer of a refractive index n
2
, which is smaller than the refractive index n
1
, having a top surface and a bottom surface, wherein the top surface of the first light transmission layer is attached to the bottom surface of the wedge-type light guide, and a light deflecting layer having a top surface attached to the bottom surface of the first light transmission layer for deflecting the incident light from the first light transmission layer toward the top surface of the wedge-type light guide.
The range of the refractive index n
1
of the wedge-type light guide is preferably approximately 1.4 through approximately 2.0, and the range of the refractive index n
2
of the first light transmission layer is preferably approximately 1.2 through approximately 1.4.
The refractive index n
1
of the wedge-type light guide is preferably approximately 1.49, and the refractive index n
2
of the first light transmission layer is preferably approximately 1.3.
The range of a top angle between the top surface and the bottom surface of the wedge-type light guide is preferably approximately 0.1 through approximately 3 degrees.
The light deflecting layer preferably includes a second light transmission layer having a refractive index, which is substantially equal to the refractive index n
1
of the wedge-type light guide, and a plurality of mirrors, each of which has a reflecting surface tilted by a selected angle from the top surface of the light deflecting layer to reflect the incident light from the first light transmission layer through the second light transmission layer toward a light path along a direction of a normal line of the top surface of the wedge-type light guide, wherein the second light transmission layer is attached to the bottom surface of the first light transmission layer, and the second light transmission layer and the plurality of mirrors are integrally formed.
The light deflecting layer includes a plurality of mirrors, each of which has a reflecting surface tilted by a selected angle from the top surface of the light deflecting layer to reflect the incident light from the first light transmission layer toward a light path along a direction of a normal line of the top surface of the wedge-type light guide, wherein the first light transmission layer and the plurality of mirrors are integrally formed.
The plurality of mirrors includes mirrors, each of which has the reflecting surface tilted by the selected angle, mirrors, each of which has the reflecting surface tilted by an angle larger than the selected angle, and mirrors, each of which has the reflecting surface tilted by an angle smaller than the selected angle.
The light source includes a fluorescent lamp, and the light reflecting surface of each of the mirrors continuously extends in a direction, which is parallel to a center line of the fluorescent lamp.
A backlight apparatus in accordance with a second aspect of the present invention includes a wedge-type light guide of a refractive index n
1
, having a top surface, a bottom surface and a side surface, a light source for directing light to the side surface of the wedge-type light guide, a light transmission layer of a refractive index n
2
, which is smaller than the refractive index n
1
, having a top surface and a bottom surface, wherein the bottom surface of the light transmission layer is attached to the top surface of the wedge-type light guide, and a plurali
Nishikai Akiko
Taira Yoichi
Yamada Fumiaki
Dudek James
McGinn & Gibb PLLC
Trepp, Esq. Robert M.
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