Flat fluorescent discharge lamp

Details Flat fluorescent discharge lamp Flat fluorescent discharge lamp

2001-12-19

2003-07-08

Patel, Vip (Department: 2879)

Electric lamp and discharge devices

With support and/or spacing structure for electrode and/or...

Supporting and/or spacing elements

C313S238000, C313S495000, C313S496000, C313S485000, C313S243000, C313S250000, C313S257000, C313S258000, C313S274000

Reexamination Certificate

active

06590319

ABSTRACT:

This application claims the benefit of Korean Patent Application No. P2001-0024861, filed in Korea on May 8, 2001, which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an LCD device, and more particularly, to a flat fluorescent discharge lamp for a back light of the LCD device.
2. Background of the Related Art
Demand for display devices is constantly increasing, and research on flat panel displays such as liquid crystal displays (LCD), plasma display panels (PDP), electroluminescent displays (ELD), vacuum fluorescent displays (VFD), etc., is being performed.
Among these displays, LCDs are most widely used because of their characteristics, such as good picture quality, lightweight, compactness, and low power consumption. Thus, making LCD's attractive substitutes to cathode ray tubes. Furthermore, because of their characteristics, LCD's are used in portable display devices.
The LCD device has been actively developed as a display device in various fields. However, picture quality in the LCD device can still be improved. Furthermore, the LCD device in addition to producing a high picture quality such as high luminance, fineness, and various colors still needs to maintain its characteristics of lightweight, thinness, and low power consumption.
In the LCD device, a light source for displaying the picture is required to obtain high picture quality. This is because the LCD device itself does not emit light. Accordingly, an external light source is required. The light source irradiates light of high luminance onto a display panel of the picture image uniformly, thereby generating high picture quality.
The LCD device includes an LCD display panel, a liquid crystal injected between upper and lower substrates, a light source providing light onto the LCD display panel, and a driving circuit for driving the LCD display panel.
In early LCD devices such as TN and STN, a small lamp is additionally mounted at the side or front of the liquid crystal display panel. However, the demand for large sized display panels and high picture quality, has made use of the back light assembly common. In the back light assembly, the light source is positioned at the rear of the liquid crystal display panel, and the picture image is displayed while the light passes through the liquid crystal display panel.
In the LCD device with a back light assembly, an electro luminescence (ELD), a light emitting diode (LED), a cold cathode fluorescent lamp (CCFL), or a hot cathode fluorescent lamp (HCFL), are used as light sources. Especially, the CCFL type is widely used in large sized color LCD devices since the CCFL has a long life, low power consumption, and is thin.
A phosphor discharge tube sealed with mercury gas and having argon and neon gases at a low temperature is used as the CCFL light source. Electrodes are formed at both sides of the tube, in which a cathode has a plate type. When a voltage is applied, charged particles within the discharge tube collide against the cathode, thereby generating secondary electrons. Subsequently, the secondary electrons excite circumferential elements to generate plasma. Then, the elements irradiate ultraviolet rays that excite the phosphor again, so that the phosphor emits visible rays.
The phosphor discharge tube is formed in two types, a direct type, and an edge type. First, in the direct type a plurality of phosphor discharge tubes are mounted below the liquid crystal display panel. In the edge type, the phosphor discharge tubes are mounted at both sides, below the liquid crystal display panel to view the picture image by light guiding and reflecting plates. To obtain uniform luminance of the picture image, a light-diffusion plate is formed between the liquid crystal display panel and the light source. In case of a large sized LCD device, the edge type is mainly used. However, the edge type has low luminance. Meanwhile, in the direct type, luminance decreases depending on temperature, and it is difficult to form the device thinly.
In the CCFL light source, mercury is a main element of the gas injected in the discharge tube. However, mercury reduces the life of the lamp when combined with metals, and reacts readily to temperature changes making mercury unsuitable as the main element for a light source. Also, with increased environmental concerns, waste disposal problems arise since mercury is a poisonous heavy metal. Accordingly, it is required to develop a new back light that addresses the aforementioned problems.
Therefore, a new back light that does not use mercury is being developed. For example, a flat fluorescent discharge lamp using xenon has been disclosed in U.S. Pat. No. 6,034,470, WO98/11596.
The basic principle of the flat fluorescent discharge lamp is as follows.
FIG. 1
is schematic view showing the structure of the basic flat fluorescent discharge lamp.
FIG. 2
shows dots generated in the flat fluorescent discharge lamp of FIG.
1
.
A plurality of electrodes
13
that apply a voltage are formed on a lower glass substrate
11
. Then, an insulating film
15
is formed on the lower glass substrate including the electrodes
13
. Subsequently, a passivation film
17
of oxide magnesium is deposited on the insulating film
15
. A phosphor film
21
is deposited on an inner surface of an upper glass substrate
23
.
The lower and upper glass substrates
11
and
23
are spaced apart from each other by a spacer
19
. A discharge gas
26
is injected between the lower and upper glass substrates
11
and
23
.
In the flat fluorescent discharge lamp, if the discharge voltage is applied to the electrode, the discharge gas is excited, thereby generating ultraviolet rays. The ultraviolet rays excite the phosphor film
21
deposited on the inner surface of the upper substrate
23
, generating visible rays, which are irradiated as the light source of the liquid crystal display panel.
However, in the flat fluorescent discharge lamp, the spacer
19
shields a portion of the phosphor film
21
. Therefore, this portion of the phosphor film is not excited by ultraviolet rays, and becomes dark. As shown in
FIG. 2
, when the flat fluorescent discharge lamp is turned on, a bright panel is partially dotted. The ultraviolet rays pass through the glass substrate at a low rate while the visible rays pass through the glass substrates at a high rate. For this reason, the ultraviolet rays generated from the injected gas do not pass through the spacer, and the ultraviolet rays do not excite the phosphor film of the spacer portion. Therefore, the visible rays are not generated in the portion of the spacer.
This reduces the uniform luminance of the back light and degrades display quality of the LCD device. To solve these problems, several light-diffusion devices such as light-diffusing plates need to be deposited. Or, the installed light-diffusion devices need to maintain some distances from a light-emitting unit of the flat fluorescent discharge lamp. However, the installation of such additional devices makes the whole width of the LCD device thick, increases the production cost, and reduces the reliability of the device.
To address these problems, a flat fluorescent discharge lamp has been recently disclosed.
FIG. 3
is a sectional view of a related art flat fluorescent discharge lamp.
FIG. 4
is a sectional view of another related art flat fluorescent discharge lamp.
In the related art flat fluorescent discharge lamp of
FIG. 3
, a plurality of electrodes
13
that apply a voltage, are formed on the lower glass substrate
11
. Then, an insulating film
15
is formed on the lower glass substrate including the electrodes
13
. Subsequently, a passivation film
17
using oxide magnesium is deposited on the insulating film
15
. A phosphor film
21
is deposited on the inner surface of the upper substrate
23
.
The lower and upper glass substrates
11
and
23
are sealed to maintain constant distances by a spacer
19
. A discharge gas
26
is injected between the lower and upper glass substrates
11
and
23

Affiliated with

Also associated with

Rating

Flat fluorescent discharge lamp does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Flat fluorescent discharge lamp, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Flat fluorescent discharge lamp will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3092084