Illumination – Light modifier – Refractor
Reexamination Certificate
2002-01-17
2003-09-02
O'Shea, Sandra (Department: 2875)
Illumination
Light modifier
Refractor
C362S026000, C362S035000, C349S065000
Reexamination Certificate
active
06612722
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a light guide panel for a backlight, which is used in a liquid crystal display device, and more particularly, the present invention relates to a light guide panel for a backlight, which minimizes loss of light introduced thereto and has various patterns on a surface thereof, thereby being able to ensure increased luminance and uniform distribution of luminance, through adjustment of a quantity of light, a scattering angle of light, etc.
2. Description of the Related Art
These days, a variety of displays have been disclosed in the art, and a typical example of these displays is a thin film transistor-liquid crystal display (TFT-LCD).
A liquid crystal display device is characterized as an optical element incapable of emitting light by itself, and therefore, in order to allow the liquid crystal display device to adequately perform its function, a backlight is provided.
Referring to
FIG. 1
, there is shown a perspective view schematically illustrating a construction of a conventional backlight for a notebook computer. As shown in
FIG. 1
, the conventional backlight
1
comprises a lamp
19
serving as a light source for emitting light, a light guide panel
13
for guiding and reflecting light emitted from the lamp
19
toward a LCD panel
18
, a first diffusing sheet
14
for diffusing at predetermined angles light exiting the light guide panel
13
, vertical and horizontal prism sheets
15
and
16
for converging and transmitting diffused light toward the LCD panel
18
, and a second diffusing sheet
17
for diffusing at preselected angles light having passed through the prism sheets
15
and
16
. The LCD panel
18
is arranged on the second diffusing sheet
17
. A reflecting sheet
12
and a case
11
are disposed under the light guide panel
13
. The reflecting sheet
12
performs a function of reflecting light rays scattered by the light guide panel
13
in the direction toward the LCD panel
18
and thereby minimizing loss of light.
In addition to the backlight
1
for a notebook computer, various backlights such as for a monitor are disclosed in the art. While the backlights can be constructed in slightly different ways depending upon use, they adopt basically the same principle. For example, while the construction of the backlight
1
for a notebook computer is slightly different from that of a backlight for a monitor in respect of sheet arrangement, they adopt basically the same operational characteristics.
The light guide panel
13
is an essential component element in the construction of the backlight
1
, and functions to scatter light emitted from the lamp
19
and transmit scattered light in the direction toward the LCD panel
18
.
Referring to
FIG. 2
, there is shown a cross-sectional view illustrating the conventional light guide panel employed in the backlight shown in FIG.
1
. As shown in
FIG. 2
, the conventional light guide panel
13
has planar lower and upper surfaces
131
and
132
. Light emitted from the lamp
19
serving as a light source is incident on the lower surface
131
, and the incident light is reflected upward. In this type of light guide panel
13
, it was found that loss of light is remarkable, and luminance and luminance distribution uniformity are poor.
To solve these problems, a great deal of efforts have been attempted toward efficient use of light, and resultingly, a technique of forming micro protrusions on a lower surface of a light guide panel through a separate printing process is disclosed in the art.
FIG. 3
is a cross-sectional view illustrating another conventional light guide panel formed with micro protrusions. As shown in
FIG. 3
, micro protrusions
133
are formed on the lower surface
131
of the light guide panel
13
. Due to the presence of the micro protrusions
133
, scattering and scattered light reflection are promoted.
However, in the case of the light guide panel
13
which is formed with the micro protrusions
133
, since the micro protrusions
133
are formed through an ultraviolet-curing printing method which uses pigments, they tend to absorb light. As a consequence, loss of light is still substantial, and it is impossible to secure high luminance and luminance distribution uniformity. Also, due to the fact that the micro protrusions
133
are formed using pigments tending to absorb light, a color intensity of light varies with the lapse of time, whereby a quality of the liquid crystal display device is deteriorated and a lifetime thereof is shortened.
To cope with these problems, attempts have been made to develop a printless type light guide panel which is manufactured without the need of implementing a printing process. In these attempts, micro protrusions are formed on a lower surface of a light guide panel by implementing an etching process on a surface of a mold or on the lower surface of the light guide panel.
In this technique for forming a light guide panel, although improvement is accomplished to some extent in terms of methodology, it is still impossible to secure high luminance and luminance distribution uniformity.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and an object of the present invention is to provide a light guide panel for a backlight, which scatters light emitted from a light source and transmits scattered light in the direction toward a LCD panel in such a way as to minimize loss of light, and at the same time, is able to perform light diffusing and converging functions.
In order to achieve the above object, according to the present invention, there is provided a light guide panel for a backlight, comprising: a plurality of groups of cells regularly or irregularly formed on at least one surface of the light guide panel, with each cell having regularly or irregularly arranged therein a plurality of micro cells.
REFERENCES:
patent: 5134549 (1992-07-01), Yokoyama
patent: 5386347 (1995-01-01), Matsumoto
patent: 5394308 (1995-02-01), Watanabe et al.
patent: 5600455 (1997-02-01), Ishikawa et al.
patent: 6099134 (2000-08-01), Taniguchi et al.
patent: 6334689 (2002-01-01), Taniguchi et al.
Lee Chang-Yong
Lee Shin-Hyung
Lim Eun-Shik
Ryu Su-Sun
Cantor & Colburn LLP
O'Shea Sandra
Vision High-Tech Co., Ltd.
Ward John Anthony
LandOfFree
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