U.S. patent application number 09/258075 was filed with the patent office on 2002-02-28 for liquid crystal display device.
Invention is credited to TAKENAKA, HIDETOSHI.
Application Number | 20020024624 09/258075 |
Document ID | / |
Family ID | 12782987 |
Filed Date | 2002-02-28 |
United States Patent
Application |
20020024624 |
Kind Code |
A1 |
TAKENAKA, HIDETOSHI |
February 28, 2002 |
LIQUID CRYSTAL DISPLAY DEVICE
Abstract
A liquid crystal display device includes a shield layer for
acoustic noise prevention between an LCD and an EL panel serving as
a backlight source for the LCD. The shield layer is fixed to the
surface of the EL panel by adhesion.
Inventors: |
TAKENAKA, HIDETOSHI;
(SAITAMA, JP) |
Correspondence
Address: |
SUGHRUE, MION, ZINN, MACPEAK & SEAS
2100 PENNSYLVANIA AVENUE, N. W.,
WASHINGTON,
DC
200373202
|
Family ID: |
12782987 |
Appl. No.: |
09/258075 |
Filed: |
February 26, 1999 |
Current U.S.
Class: |
349/110 |
Current CPC
Class: |
G02F 1/133604 20130101;
G02F 1/133308 20130101; G02F 1/133334 20210101; G02F 2202/28
20130101 |
Class at
Publication: |
349/110 |
International
Class: |
G02F 001/133 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 27, 1998 |
JP |
047714/1998 |
Claims
What is claimed is:
1. A liquid crystal display device comprising a shield layer for
acoustic noise prevention between an LCD and an EL panel serving as
a backlight source for said LCD.
2. A device according to claim 1, wherein said shield layer is
fixed to a surface of said EL panel by adhesion.
3. A device according to claim 1, wherein said shield layer is
fixed to said LCD through a double-coated tape by adhesion.
4. A device according to claim 1, wherein said shield layer is a
transparent electrode layer connected to ground.
5. A device according to claim 4, wherein said transparent
electrode layer is formed on one entire surface of said EL
panel.
6. A device according to claim 4, wherein said transparent
electrode layer has an impedance set to less than several ten
k.OMEGA..
7. A device according to claim 1, wherein said shield layer is a
conductor selected from a group consisting of an ITO foil, an
aluminum foil and silver foil.
8. A liquid crystal display device comprising a ground plate
between an LCD and an EL panel serving as a backlight source for
said LCD.
9. A device according to claim 8, wherein said ground plate is
formed by forming a transparent electrode layer on one surface of a
PET film.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a display device and, more
particularly, to an improvement in a liquid crystal display device
having an electroluminescence (to be referred to as an EL
hereinafter) panel as a backlight source.
[0003] 2. Description of the Prior Art
[0004] An EL panel is conventionally utilized as a backlight source
for a liquid crystal display device. When an EL panel is used as a
backlight source, the circuit portions of the display device
mounted on the circuit board must be protected from electromagnetic
wave noise generated by the EL panel.
[0005] In a liquid crystal display device disclosed in Japanese
Unexamined Patent Publication No. 9-152605, as shown in FIG. 1, an
EL panel 52 is placed on a circuit board 51 by stacking, a liquid
crystal panel 54 is placed on an emission surface 52a side of the
EL panel 52 by stacking, and a frame 55 is mounted on the surface
of the liquid crystal panel 54. A shield layer 53 is formed on the
lower surface of the EL panel 52. Since the shield layer 53 is
provided between the EL panel 52 and circuit board 51, the
electromagnetic wave noise generated by the EL panel 52 is
prevented from adversely affecting the respective circuits on the
circuit board 51.
[0006] In the liquid crystal display device of this type, the
electromagnetic wave noise generated by the EL panel can be
prevented from adversely affecting the respective circuits on the
circuit board. If, however, the liquid crystal display device is
applied to a portable terminal such as a cellular phone or PHS,
since a display 33 is arranged near an ear piece 32, as shown in
FIG. 2, the acoustic noise generated by the EL panel increases due
to the resonance of the display 33. Even slight noise becomes
offensive to the ear to discomfort the user.
SUMMARY OF THE INVENTION
[0007] The present invention has been made in consideration of the
above situation of the prior art, and has its object to provide a
liquid crystal display device in which noise output from a speech
reception port and a display due to acoustic noise from an EL panel
can be decreased.
[0008] In order to achieve the above object, according to the first
main aspect of the present invention, there is provided a liquid
crystal display device comprising a shield layer for acoustic noise
prevention between an LCD and an EL panel serving as a backlight
source for the LCD.
[0009] In addition to the first main aspect, the present invention
also has auxiliary aspects as follows.
[0010] According to the first auxiliary aspect, the shield layer of
the first main aspect is fixed to a surface of the EL panel by
adhesion.
[0011] According to the second auxiliary aspect, the shield layer
of the first main aspect is fixed to the LCD through a
double-coated tape by adhesion.
[0012] According to the third auxiliary aspect, the shield layer of
the first main aspect is a transparent electrode layer connected to
ground.
[0013] According to the fourth auxiliary aspect, the transparent
electrode layer of the third auxiliary aspect is formed on one
entire surface of the EL panel.
[0014] According to the fifth auxiliary aspect, the transparent
electrode layer of the third auxiliary aspect has an impedance set
to less than several ten k.OMEGA..
[0015] According to the sixth auxiliary aspect, the shield layer of
the first main aspect is a conductor selected from a group
consisting of an ITO foil, an aluminum foil and silver foil.
[0016] In order to achieve the above object, according to the
second main aspect of the present invention, there is provided a
liquid crystal display device comprising a ground plate between an
LCD and an EL panel serving as a backlight source for the LCD.
[0017] The ground plate of the second main aspect is formed by
forming a transparent electrode layer on one surface of a PET
film.
[0018] According to the present invention having the aspects
described above, an electromagnetic wave preventive ground plate
having a transparent electrode layer or transparent electrode
connected to ground is placed between an LCD and an EL panel to
shield an electric field that varies in accordance with a drive
frequency generated by the EL panel. Resonance (acoustic noise)
between the EL panel and the transparent electrode of the LCD can
accordingly be decreased. As a result, noise output from the ear
piece and display can be decreased.
[0019] The above and many other objects, features and advantages of
the present invention will become manifest to those skilled in the
art upon making reference to the following detailed description and
accompanying drawings in which preferred embodiments incorporating
the principle of the present invention are shown by way of
illustrative examples.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is an exploded perspective view showing the main
components of a conventional liquid crystal display device;
[0021] FIG. 2 is a front view showing a conventional cellular
phone;
[0022] FIG. 3 is an exploded perspective view showing the main
components of a liquid crystal display device according to the
present invention;
[0023] FIG. 4 is a schematic sectional view of an EL panel and an
LCD shown in FIG. 3 according to an embodiment; and
[0024] FIG. 5 is a schematic sectional view of a modification of an
EL panel and an LCD.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0025] Several preferred embodiments of the present invention will
be described with reference to the accompanying drawings.
[0026] FIG. 3 is an exploded perspective view of the main
components of a display device according to an embodiment.
[0027] Referring to FIG. 3, the display device of this embodiment
has a circuit board 23 on which mounting parts are mounted at
predetermined positions. The circuit board 23 and the lower surface
of an EL panel 1 are adhered to each other through a double-coated
tape 22a. The double-coated tape 22a is used for fixing the EL
panel 1 to the circuit board 23. When the EL panel 1 is firmly
fixed to the circuit board 23 with the double-coated tape 22a,
vibration of the EL panel 1 can be suppressed. The EL panel 1 is
provided with a ground terminal 25, an upper surface electrode
terminal 26, and a lower surface electrode terminal 27. A
transparent electrode layer (not shown) formed on the upper surface
of the EL panel 1, and an LCD 2 are adhered to each other through a
double-coated tape 22b. The double-coated tape 22b is employed to
fix the LCD 2 and is preferably a thin tape having a thickness of
about 0.1 .mu.m (micrometer).
[0028] FIG. 4 shows the sectional arrangement of the EL panel 1 and
LCD 2 shown in FIG. 3.
[0029] Referring to FIG. 4, the EL panel 1 is constituted by a PET
film 7, a transparent electrode layer 8, an emission layer 9, an
insulator layer 10, a rear electrode layer 11, and an insulating
layer 12. The PET film 7 is formed of polyester, and the
transparent electrode layer 8 is formed by forming a thin
indium-tin oxide (ITO) film on the surface of the PET film 7 by
vapor deposition. The emission layer 9 is formed of ZnS (zinc
sulfide) or the like, and the insulator layer 10 is formed of an
insulator such as a rubber-based resin. The rear electrode layer 11
is formed of carbon, and the insulating layer 12 is formed by
overcoating such as resist printing.
[0030] An acoustic noise preventive shield layer, preferably a
transparent electrode layer 6, connected to ground through the
ground terminal 25 is formed on the surface of the EL panel 1. The
transparent electrode layer 6 is desirably formed on the surface of
the EL panel 1 as large as possible. Hence, it is preferable to
form the transparent electrode layer 6 on the surface of a large
PET film by vapor deposition and to pattern it into the shape of
the EL panel 1, so that it is present on the entire surface of the
EL panel 1. The impedance of the transparent electrode layer 6,
i.e., the resistance, is desirably set to a low value, e.g., less
than several ten k.OMEGA.. Although a conductor such as an aluminum
foil or a silver foil having a low resistance can be used as the
transparent electrode layer 6, it decreases the function of the LE
as the backlight. Therefore, a transparent electrode layer having a
high optical transmission such as, for example, an ITO foil is
desirably used.
[0031] An inverter circuit 3 is controlled by a CPU (not shown).
For example, when the user operates a switch (not shown), the
inverter circuit 3 boosts the voltage of a DC power supply 4 and
converts the voltage to an AC signal. The AC signal is applied to
the EL panel 1 through the upper surface electrode terminal 26 and
lower surface electrode terminal 27 to cause it to emit light. The
voltage of the output signal from the inverter circuit 3 is usually
as high as AC 100 V, and a drive frequency in an audio frequency
band of about 200 Hz to 600 Hz is used.
[0032] The LCD 2 is constituted by a glass plate 13 having a
polarizing film, a transparent electrode layer 14, a liquid crystal
15, a transparent electrode layer 16, and a glass plate 17 having a
polarizing film, and is connected to a drive circuit 5.
[0033] In this arrangement, in the EL panel 1, when the output
signal from the inverter circuit 3 is applied to the transparent
electrode layer 8 and rear electrode layer 11, an electric field
moving in the vertical direction (to the upper and lower
directions) is generated by the transparent electrode layer 8 and
rear electrode layer 11 to cause the emission layer 9 to emit
light. Although the electric field generated by the transparent
electrode layer 8 of the EL panel 1 is also generated in the
direction toward the LCD 2, it is shielded as it is attracted by
ground due to the low-impedance transparent electrode layer 6
formed on the surface of the EL panel 1.
[0034] The present invention has been described so far by way of
its preferred embodiment. The liquid crystal display device
according to the present invention is not limited to the above
embodiment. For example, although the transparent electrode layer 6
connected to ground is formed on the surface of the EL panel 1 in
the liquid crystal display device of the above embodiment, a ground
plate 19, on which a transparent electrode layer 21 formed on one
surface of a PET film 20 is formed, may be placed between an LCD 2
and an EL panel 18, as shown in the modification of FIG. 5. The
transparent electrode layer 21 is connected to ground. The ground
plate 19 must be fixed by, e.g., adhering it to the EL panel 18. In
the liquid crystal display device of this modification, the
transparent electrode layer 21 is formed on the separate PET film
20 by vapor deposition. Although this liquid crystal display device
is inferior to that shown in FIG. 4 in terms of cost, optical
transmission, thickness, and assembly easiness, it is excellent as
a temporary countermeasure in the manufacturing process.
[0035] In the embodiment and its modification described above, the
EL panel is fixed to the circuit board with the double-coated tape.
Alternatively, the EL panel may be fixed by adhering it to a rigid
substrate (base).
* * * * *