Liquid crystal cells – elements and systems – Particular structure – Particular illumination
Reexamination Certificate
1999-07-13
2001-09-11
Dudek, James A. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Particular illumination
C349S068000, C349S069000, C362S035000, C362S084000
Reexamination Certificate
active
06288761
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the structure of the backlight of an LCD (liquid crystal display), in particular, the structure by which the frame portion of the display section can be narrowed and the device's weight can be reduced.
This application is based on Patent Application No. Hei 10-220782, filed in Japan, the contents of which are incorporated herein by reference.
2. Description of the Related Art
The LCD, used as a display device, is mounted in a variety of electronic devices. A laptop (or notebook) personal computer is a typical electronic device employing a large-size liquid display screen. In recent laptop personal computers, the main screen size has been standardized to “A4 size” or “B5 size”, and there is competition to develop thinner and lighter screens at these standard sizes. Development is being carried out to increase the area of the LCD itself within the limited main screen size. In order to increase the area of the LCD, it is important to determine how the outer edge of the LCD screen, that is, the frame portion of the main screen, can be narrowed.
FIG. 4
is a general perspective view showing the backlight portion of a conventional transmission-type LCD, and
FIG. 5
is a sectional view thereof.
As shown in
FIGS. 4 and 5
, the backlight of such a conventional transmission-type LCD generally comprises light-introducing plate
23
for introducing light, input from an end face the plate, in a manner such that the LCD panel is irradiated by the light, cold cathode tube
26
for radiating light towards the inside of the light-introducing plate
23
; reflector
27
for effectively reflecting the light radiated from the cold cathode tube
26
so as to direct the reflected light towards the end face of the light-introducing plate
23
; diffusion plate
30
, disposed on the upper face of the light-introducing plate
23
, for diffusing the light (introduced from the light-introducing plate
23
) towards the outside; and reflection plate
25
, attached to the bottom face of the light-introducing plate
23
, for reflecting the light transmitted through the light-introducing plate
23
so as to direct the reflected light towards the front face. Reference numeral
21
indicates an LCD panel, and reference numeral
22
indicates a display section.
In the above structure, lower-voltage electrode
26
b
and higher-voltage electrode
26
a
are provided at both ends of the cold cathode tube
26
, and the lower-voltage electrode
26
b
is connected with connection (wiring) line
31
. In order to easily connect the cold cathode tube
26
with an electric source, the connection line
31
is extended to the connection point of the higher-voltage electrode
26
a
and such an arrangement prevents the narrowing of the screen frame.
In order to make the LCD thin and to make the screen frame narrow in the above structure of the backlight, Japanese Unexamined Patent Application, First Publication, No. Hei 9-230341 discloses an arrangement (shown in
FIG. 6
) in which a sheet-type connection line
31
is adopted and is disposed on the upper face of the light-introducing plate
23
, thereby reducing the size and weight of the device.
However, in the above structure, if the cold cathode tube
26
and reflector
27
are disposed in the display area corresponding to the display section
22
of LCD panel
21
, the upper portion of the reflector
27
is not irradiated, so that the cold cathode tube
26
and reflector
27
must be disposed outside the above display area. Therefore, it is difficult to further narrow the frame of the LCD.
SUMMARY OF THE INVENTION
In consideration of the above circumstances, an objective of the present invention is to provide a novel structure for the backlight of an LCD, by which the frame portion of the screen can be further narrowed and the weight of the LCD can be reduced.
Therefore, the present invention provides a backlight of a liquid crystal display, arranged in the display area corresponding to a display section of the liquid crystal display in a manner such that the backlight partially overlaps the display area, the backlight comprising:
a cold cathode tube which is disposed along a part of a circumferential area of the display section;
a light-introducing plate made of a light-transmitting material, an end face of which faces the cold cathode tube;
a reflector for surrounding the cold cathode tube and reflecting light radiated from the cold cathode tube; and
an electro-luminescence lamp provided between the display section and the reflector, so as to radiate a part of the display section which cannot be irradiated via the light-introducing plate.
According to the above structure, the cold cathode tube and the and the reflector are arranged in the display area corresponding to the display section, and the electro-luminescence lamp is provided between the display section and the reflector. Therefore, a part of the display section which cannot be irradiated using the cold cathode tube can be irradiated by the electro-luminescence lamp; thus, the frame portion of the LCD can be much narrower in comparison with conventional LCDs. In addition, the light-introducing plate can be smaller, thereby reducing the weight of the LCD.
Preferably, the electro-luminescence lamp is arranged in a manner such that the electro-luminescence lamp overlaps the whole circumference area of the display section. Accordingly, it is possible to prevent this circumference area from getting dark and the brightness of the LCD can further be more uniform.
The backlight may comprise a first diffusion plate, disposed above the light-introducing plate, for diffusing light incident from the light-introducing plate.
The backlight may further comprise a second diffusion plate for diffusing light, which is arranged in a manner such that the whole area of the first diffusion plate and the electro-luminescence lamp is covered with the second diffusion plate.
In the above structure, a dot pattern may be formed at the lower face side of the light-introducing plate so as to diffuse and reflect light introduced to said lower face side.
REFERENCES:
patent: 5143433 (1992-09-01), Farrell
patent: 5339179 (1994-08-01), Rudisill et al.
patent: 5396406 (1995-03-01), Ketchpel
patent: 5617251 (1997-04-01), Ohta et al.
patent: 5748270 (1998-05-01), Smith
patent: 6099134 (2000-08-01), Taniguchi et al.
patent: 6111622 (2000-08-01), Abileah
patent: 62-38623 (1987-03-01), None
patent: 62-38624 (1987-03-01), None
patent: 5-223915 (1990-09-01), None
patent: 4-37718 (1992-02-01), None
patent: 8-166589 (1996-06-01), None
patent: 9-230341 (1997-09-01), None
patent: 10-125461 (1998-05-01), None
Dudek James A.
NEC Corporation
Schechter Andrew
Scully Scott Murphy & Presser
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