Direct-type back light device

Details Direct-type back light device Direct-type back light device

2002-06-27

2004-10-19

O'Shea, Sandra (Department: 2875)

Illumination

Plural light sources

With modifier

C362S249070, C362S240000, C362S225000

Reexamination Certificate

active

06805464

ABSTRACT:

The present invention claims the benefit of the Korean Application No. P2001-68567 filed in Korea on Nov. 5, 2001, which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a back light device, and more particularly, to a direct-type back light device for a liquid crystal display (LCD) device.
2. Discussion of the Related Art
In general, ultra thin sized flat panel displays having a display screen with a thickness of several centimeters or less, and in particular, flat panel LCD devices, are commonly used as monitors for notebook computers, spacecraft, and aircraft. A passive luminescent LCD includes a back light device provided at a rear of an LCD panel and is commonly used as a light source. However, the back light device is inefficient due to its weight, power consumption, and overall thickness. The back light device used as a light source of an LCD is commonly formed as a plurality of cylindrical fluorescent lamps arranged along a first direction and spaced apart from each other along a second direction perpendicular to the first direction.
The back light device may be defined as one of two distinct categories including a direct-type back light device and a light guiding plate-type back light device. In the direct-type back light device, a fluorescent lamp is arranged on a flat panel, and is spaced from the LCD panel, thereby preventing a shape of the fluorescent lamp to be displayed on a LCD panel. In addition, a light-scattering means is necessary in order to provide uniform light distribution for the LCD panel. Accordingly, an overall size of the LCD device will be increased because of the requirements of the direct-type back light device. Moreover, with the development of large-sized LCD panels, a light-emitting area of the back light device increases. Accordingly, a light-scattering means should be provided having a sufficient thickness to ensure that the light-emitting area is flat.
In the light guiding plate-type back light device, a fluorescent lamp is provided at one side of a light guiding plate such that light is dispersed onto an entire surface of the LCD panel. However, since the fluorescent lamp is provided to pass through the one side of the light guiding plate, low luminance of the LCD panel arises. Accordingly, advanced optical design and processing technologies are necessary to ensure uniform distribution of luminous intensity of the fluorescent lamp.
The direct-type back light device and the light guiding plate-type back light device are problematic for each of there unique shortcomings. For example, the direct-type back light device is commonly used for LCD devices, such as monitors for personal computers or televisions, where brightness is considered more important than overall thickness of the type of back light device. The light guiding plate-type back light device is commonly used for LCD devices, such as notebook computers, where overall thickness of the type of back light device is important.
FIG. 1
is a perspective view of a direct-type back light device according to the related art, and
FIG. 2
is a perspective view of a connector according to the related art. In
FIG. 1
, the direct-type back light device includes a plurality of luminescent lamps
1
, an outer case
3
that fixes and supports the luminescent lamps
1
, and light-scattering sheets
5
a
,
5
b
and
5
c
arranged between the luminescent lamps
1
and an LCD panel (not shown).
Each of the luminescent lamps
1
are commonly referred to as cold cathode fluorescent lamps (CCFL's), and act as a light source of an LCD device. The opposite ends of the luminescent lamp
1
are fit into grooves formed at both sides of the outer case
3
.
The outer case
3
includes a reflecting plate
7
formed on an innermost side, and is arranged to focus light emitted from each of the luminescent lamps
1
onto a display part of the LCD panel (not shown), thereby enhancing light efficiency.
The light scattering sheets
5
a
,
5
b
, and
5
c
prevent an image of the luminescent lamps
1
from being displayed onto a display screen of the LCD panel (not shown) and provide uniform distribution of the emitted light from the luminescent lamps
1
. In addition, the light scattering sheets
5
a
,
5
b
, and
5
c
may include a plurality of diffusion sheets and plates, thereby enhancing a light scattering effect.
In
FIG. 2
, each of the luminescent lamps
1
includes electrodes
2
a
and
2
b
arranged at opposite ends of the lamp
1
. The luminescent lamps
1
emit light when a power source is supplied to the electrodes
2
a
and
2
b
via power lines
9
a
and
9
b
, respectively. The power lines
9
a
and
9
b
are connected to a connector
11
, and the connector
11
is connected to a driving circuit (not shown). Accordingly, each luminescent lamp
1
requires a separate connector
11
. In addition, one of the power lines
9
a
and
9
b
is curved downward toward the outer case
3
and is connected to the connector
11
.
However, the direct-type back light device according to the related art is problematic. For example, since the connector
11
is connected to the power lines
9
a
and
9
b
of the luminescent lamp
1
, a separate connector
11
is required for each luminescent lamp
1
. Accordingly, a total number of power lines
9
a
and
9
b
and connectors
11
may lead to complicated fabricating processes. Working efficiency of the direct-type back light device deteriorates since one of the power lines
9
a
and
9
b
is bent to reduce the total thickness of the back light device. In addition, manufacturing time increases and productivity deteriorates since separate fabrication processes are required.
In addition, a hole is formed to pass through the outer case so that the electrode is connected with the connector. Both electrodes of the luminescent lamp are fitted into the hole so that they are exposed outside the outer case. For this reason, efficiency of the manufacturing process is reduced and it is not easy to repair and maintain the luminescent lamp.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a direct-type back light device that substantially obviates one or more problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a direct-type back light device having uniform luminance.
Another object of the present invention is to provide a direct-type back light device that facilitates maintenance, replacement and repair.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described, a direct type back light device includes a plurality of luminescent lamps, each having first and second opposite ends, first and second lower supports separated at a constant interval corresponding to a length of each of the luminescent lamps, the first and second lower supports each have a plurality of grooves for receiving one of the first and second opposite ends of the luminescent lamps to fix and support the luminescent lamps in parallel and conductive layers for supplying power to the luminescent lamps, and first and second upper supports formed to oppose the first and second lower supports, each of the first and second upper supports having grooves and conductive layers corresponding to the grooves and conductive layers of the first and second lower supports.
In another aspect, a direct-type back light device includes a plurality of luminescent lamps, each having first and second opposite ends, first and second lower supports separated at a constant interval corresponding to a length of the

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