Electric lamp and discharge devices – With luminescent solid or liquid material – With gaseous discharge medium
Reexamination Certificate
2001-06-07
2003-03-25
Day, Michael H. (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
With gaseous discharge medium
C313S634000, C313S245000, C313S610000
Reexamination Certificate
active
06538373
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a cold cathode fluorescent lamp suitable for a liquid crystal display, and further to a back-light emitting device having the cold cathode fluorescent lamp, and still further to a note-type personal computer having the back-light emitting device.
2. Description of the Related Art
In these days, a liquid crystal display mounted on a note-type personal computer is required to have 800×600 pixels or 1024×768 pixels both having a high resolution. Along with an increase in a resolution, a liquid crystal display becomes larger in size. For instance, a size of a liquid crystal display screen has changed from 12.1 to 13.3, and then, from 13.3 to 14.1.
However, a note-type personal computer has a restriction that a size thereof does not exceed A4 size or A4 file size. In addition, a note-type personal computer is required to have a smaller weight. As a result, there are many problems to be solved with respect to a liquid crystal display to be mounted on a note-type personal computer.
The first problem is that a liquid crystal display has to have a smaller thickness and a smaller weight.
The second problem is that a distance between a liquid crystal screen and an outer edge of a liquid crystal display is shortened in order to make it possible to incorporate a larger screen into a limited floor area of a note-type personal computer. In other words, a smaller-framed screen is required.
The third problem is that an arrangement of parts except a liquid crystal display, such as an inverter, is altered to thereby prevent an increase in a floor area of a note-type personal computer.
FIGS. 1 and 2
partially illustrate conventional note-type personal computers.
The conventional note-type personal computer illustrated in
FIG. 1
is comprised of a first body
16
a
including a structure acting as a computer and an input means such as a keyboard, a second body
16
b
including a display screen
17
which has an outer periphery
15
and on which images are displayed, a hinge structure
11
formed between the first and second bodies
16
a
and
16
b
for connecting the second body
16
b
to the first body
16
a
so that the second body
16
b
is rotatable relative to the first body
16
a
, an inverter
12
housed in the hinge structure
11
almost at the center, and a cold cathode fluorescent lamp
5
housed in the second body
16
b
at a bottom.
The cold cathode fluorescent lamp
5
includes first and second terminal electrodes
1
and
4
at opposite ends. The first terminal electrode
1
is electrically connected to a low voltage cable
10
through both a lead-in wire
6
a
and a thin wire
7
, and the low voltage cable
10
is connected to a low voltage terminal
14
of the inverter
12
. The second terminal electrode
4
is electrically connected to a high voltage cable
9
through a lead-in wire
6
b
, and the high voltage cable
9
is connected to a high voltage terminal
13
of the inverter
12
.
The conventional note-type personal computer illustrated in
FIG. 2
has the same structure as that of the note-type personal computer illustrated in FIG.
1
. The note-type personal computer illustrated in
FIG. 1
is different from the note-type personal computer illustrated in
FIG. 2
with respect to a location of a wire port
8
through which low and high voltage cables
9
and
10
extend. Specifically, the second body
16
b
of the note-type personal computer illustrated in
FIG. 1
is formed at a bottom corner with the wire port
8
, whereas the second body
16
b
of the note-type personal computer illustrated in
FIG. 2
is formed at a center of a bottom edge with the wire port
8
.
The reasons why it is difficult to render a frame around the display screen smaller are in a conventional note-type personal computer as follows. If a frame around the display screen is made smaller, the cold cathode fluorescent lamp
5
is located just in the close vicinity of, or at the rear of the display screen
17
. Hence, when the cold cathode fluorescent lamp
5
is turned on, fluorescent lights pass directly through the display screen
17
. In addition, there has to exist a space just below the display screen
17
for housing therein wires connecting the first and second terminal electrodes
1
and
4
to the inverter
12
. Hence, the cold cathode fluorescent lamp cannot avoid to be located closer to the display screen
17
by a distance corresponding to the above-mentioned space, which makes it more difficult to form the frame smaller.
As a solution to the above-mentioned problems, there is employed the thin wire having a diameter of about 0.3 mm for connecting the lead-in wire
6
a
and the low voltage cable
10
, to thereby narrow the above-mentioned space for locating the cold cathode fluorescent lamp
5
remoter from the display screen
17
.
If the display screen
17
is made larger in size, a back-light emitting device has to be made larger accordingly, and as a result, a cold cathode fluorescent lamp as a back-light source has to be made longer accordingly.
A cold cathode fluorescent lamp is presently widely used as a back-light source for a liquid crystal display, because a cold cathode fluorescent lamp has many advantages that it generates a small amount heat, it has a relatively long lifetime, and an electrode structure is simple, and hence is able to be formed smaller, contributing to formation of a liquid crystal display in a smaller size.
However, if a cold cathode fluorescent lamp were designed to have a smaller diameter and a longer length, a break-down voltage and a discharge voltage would be both increased. Specifically, if a display screen has a width across corners of 14 inches, a cold cathode fluorescent lamp would have a length exceeding 280 mm, and a break-down voltage and a discharge voltage of a cold cathode fluorescent lamp having a diameter of 2.0 mm would reach about 1200 Vrms and 650 Vrms, respectively.
A hot cathode fluorescent lamp has a lower discharge voltage than that of a cold cathode fluorescent lamp, but has shortcomings that a filament electrode emitting thermoelectrons which cause light-emission generates heat, a hot cathode fluorescent lamp cannot be formed smaller in diameter because electrodes cannot be formed smaller in size, and a hot cathode fluorescent lamp has a short lifetime. Accordingly, a hot cathode fluorescent lamp is scarcely used as a back-light source of a liquid crystal display used for a note-type personal computer.
As mentioned earlier, the note-type personal computer illustrated in
FIG. 1
employs the thin wire
7
for connecting the lead-wire
6
a
to the low voltage cable
10
in order to make a frame around the display screen
17
smaller. However, since the high and low voltage cables
9
and
10
are designed to extend through the wire port
8
formed at a corner of the second body
16
b
, there is paused a problem that those high and low voltage cables
9
and
10
cause the second body
16
b
larger in size.
The reason is as follows. The high voltage cable
9
has to have a high resistance to high voltages, and hence, cannot avoid to have a relatively large diameter. For this reason, if the wire port
8
through which the high voltage cable
9
is introduced is formed at a corner of the second body
16
b
, it would be necessary to make a space A between the second body
16
b
and the outer periphery
15
of the display screen
17
for housing the cables
9
and
10
therein. As a result, the second body
16
b
cannot avoid to become larger in size to a degree corresponding to the space A.
In the note-type personal computer illustrated in
FIG. 2
, the wire port
8
through which the high and low voltage cables
9
and
10
are introduced is formed at a center of a bottom edge of the second body
16
b
. Hence, a space for housing the high and low voltage cables
9
and
10
therein, such as the space A illustrated in
FIG. 1
, is cancelled by the hinge structure
11
, and thus, the above-mentioned problem about the space A is solved in the note-typ
Day Michael H.
Haynes Mack
NEC Corporation
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