Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
1998-02-27
2001-01-30
Vu, David (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C315S224000, C349S070000
Reexamination Certificate
active
06181071
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display panel used in a display or the like of a computer, and more particularly, to a thinner display panel.
FIG. 14
is a basic configuration view of a conventional liquid crystal panel unit of a back light type described in, for example, page 337 of an additional edition of a monthly Semiconductor World “'95 Latest Liquid Crystal Process Art”. Referring to the drawing, numeral
1
is a polarizer and numeral
2
is a liquid crystal panel composed of a color filter
3
and an array substrate
4
. Numeral
5
is a driving circuit for image displaying connected with the array substrate
4
. A back light comprises a diffusion sheet
6
for scattering and equalizing light, a light guide plate
7
, a reflective sheet
8
placed on the reverse side of the light guide plate
7
, a cold cathode tube (lamp)
9
, and a reflective plate
10
. Numeral
30
is an inverter for providing AC power of high voltage to the lamp
9
.
FIG. 15
is a sectional view showing a comparative embodiment for explaining effects of the present invention. In
FIG. 15
, numeral
1
is a polarizer (thickness: 0.21 mm), and numeral
2
is a liquid crystal panel composed of a color filter
3
(thickness: 0.5 mm) and an array substrate
4
(thickness: 0.4 mm). Numeral
6
is a diffusion sheet (thickness: 0.14 mm); numeral
7
a light guide plate (thickness: 2 mm); numeral
8
a reflective sheet (thickness: 0.125 mm); numeral
9
a lamp (diameter: 2 mm); and numeral
10
an Ag reflective plate (thickness: 0.05 mm), respectively. Further, numeral
11
is an insulating film (thickness: 0.1 mm); numeral
12
a back metal plate (thickness: 3 mm) of a metal housing; numeral
13
a metal housing frame; numeral
14
a front metal plate (thickness: 3 mm) of the housing; numeral
15
a decorative sheet (thickness: 0.2 mm); numeral
16
two prism sheets each having a thickness of 0.16 mm; and numeral
17
a bonding material (thickness: 0.1 mm) respectively. Further, numerals
34
to
36
are a groove for allowing a low voltage wiring of the lamp to pass, plastic mold and a frame coated with black ink for preventing directly reflected light from the lamp from being observed, respectively. In
FIG. 15
, sizes of t11 to t15 and t17 to t22 are 0.5 mm (t11), 3.795 mm (t12), 0.3 mm (t13), 0.4 mm (t14), 0.2 mm (t5), 0.5 mm (t17), 3.995 mm (t18), 0.3 mm (t19), 1.62 mm (t20), 2 mm (t21) and 0.375 mm (t22: 0.1 mm of bonding material +0.125 mm of reflective sheet +0.05 mm of Ag sheet +0.1 mm of insulating film), respectively.
The operation of the panel unit will be described. A DC power of approximately 5 through 12 V to be provided from a battery is converted into an AC power of 40 through 200 kHz in frequency, and approximately 500 through 1500 V in effective voltage by the inverter
30
and is applied to the high voltage terminal of the lamp
9
. The other end is earthed to allow the lamp
9
to emit light with potential distribution shown in FIG.
5
. The light emitted from the lamp
9
enters into the light guide plate
7
and spreads on the whole face of the light guide plate
7
while being reflected by the reflective sheet
8
. At this time, the periphery of the lamp
9
is surrounded by a reflective plate
10
so as to let more light enter into the light guide plate
7
without waste. In order to raise the reflectance, a sheet with silver being spattered on it is used as a reflective plate
10
. Thus, a capacity coupling is formed among the lamp
9
, silver reflective plate
10
, and a housing metal portion adjacent thereto, and a leak pass of the high frequency power applied to the cold cathode tube is formed. The scattered dots are formed on the reverse face of the light guide plate
7
. The light scattered at the reverse face of the light guide plate
7
and coming from the front face of the light guide plate
7
is scattered by the diffusion sheet
6
to be equalized. Furthermore, the light enters into a liquid crystal after the light have been throttled in a direction vertical to a panel face by a prism sheet. In the liquid crystal panel, after the incident light has been polarized by the polarizer
1
, the polarization direction of the light is rotationally shifted for each dot in accordance with the image signal at the liquid crystal panel
2
to which the voltage has been applied with the driving circuit
5
, and the light passes through a color filter. Finally, only the light rotated by 90 degrees in the polarization direction by a second polarization plate
1
which is an analyzer, can be transmitted.
In order to form a thin type liquid crystal display panel including an external panel, the liquid crystal display of a back light type has the following problems simultaneously with a problem of thinning.
(1) measures against electromagnetic injuries (EMI)
(2) reduction of consumption power (2 W or lower)
(3) impact resistance (not broken with impact of 200 G)
Accordingly, an object of the present invention is, in a panel module using a metal housing with a large impact resistance which becomes a stable ground and has an electromagnetic shielding function, to restrain increase of leakage current due to thinning from between a back light lamp and a panel housing to improve the equalization of lamp radiation, thereby reducing the load of a high frequency current supply circuit.
SUMMARY OF THE INVENTION
A display panel apparatus according to a first configuration of the present invention comprises a transmission type liquid crystal panel, a lamp provided adjacent to at least one side of a light guide plate for guiding illumination light to the crystal panel, a high frequency current supply for providing a lighting current to the lamp, a reflective plate provided to encircle the lamp to introduce illumination light of the lamp to the light guide plate, and a housing composed of a metal thin plate; wherein each portion of the housing is connected with a common electric potential, and a portion having a shape departing from the lamp is formed in a portion of the housing adjacent to the lamp.
A display panel apparatus according to a second configuration of the present invention comprises a transmission type liquid crystal panel, a lamp provided adjacent to at least one side of a light guide plate for guiding illumination light to the crystal panel, a high frequency current supply for providing a lighting current to the lamp, a reflective plate provided to encircle the lamp to introduce illumination light of the lamp to the light guide plate, and a housing composed of a metal thin plate; wherein each portion of the housing is connected with a common electric potential, and an opening is formed in a portion of the housing adjacent to the lamp.
In a display panel apparatus according to a third configuration of the present invention, the housing is formed of an insulating thin plate with a metal net being embedded in the plate, and each portion of the housing is connected with a common electric potential.
In a display panel apparatus according to a fourth configuration of the present invention, the reflective plate is composed of an insulating body with an insulating reflection material being applied thereon.
In a display panel apparatus according to a fifth configuration of the present invention, the reflective plate is formed with the use of a metal film divided into a plurality of areas which are electrically insulated to one another.
In a display panel apparatus according to a sixth configuration of the present invention, a common mode choke is inserted between the high frequency current supply and the lamp.
In a display panel apparatus according to a seventh configuration of the present invention, the high frequency current supply comprises a current supply of a type for alternately applying positive and negative voltages in antiphase to both ends of the lamp.
In a display panel apparatus according to a eighth configuration of the present invention, the swollen part of the housing is provided only in position opposite to both e
Kawabe Shin
Kumagai Takashi
Matsumoto Sadayuki
Umesaki Mitsumasa
Yuuki Akimasa
Mitsubishi Denki & Kabushiki Kaisha
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Vu David
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