Electricity: circuit makers and breakers – Electric switch details – Indicators
Reexamination Certificate
2002-01-16
2004-01-20
Friedhofer, Michael (Department: 2832)
Electricity: circuit makers and breakers
Electric switch details
Indicators
C200S512000, C345S173000
Reexamination Certificate
active
06680448
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a touch panel for a display device which is disposed close to a display surface of a display device such as a liquid crystal display device and generates a specified signal corresponding to a position touched when an operator touches a desired position on a panel surface with a pen or a finger based on information displayed on the display surface.
2. Description of the Related Art
Since the panel surface of this type of a touch panel can be used for both display and input of information, the utilization factor of the panel surface is increased, and the touch panel is in demand for compact information processors and communication equipment, in particular, mobile communications terminals.
FIG. 2
is a sectional view of a conventional touch panel (disclosed in FIG. 2 in Japanese Unexamined Patent Application Publication No. 2000-187197).
As shown in
FIG. 2
, a touch panel
10
basically comprises a pair of resistive layers (fist and second resistive layers)
12
and
13
disposed opposite to each other across a plurality of insulating dot spacers
11
, and a flat transparent plate protecting the second resistive layer, for example, a transparent glass plate
16
. The second resistive layer
13
is laid on the glass plate
16
while the touch panel
10
is disposed close to the display device
30
such that the glass plate
16
faces the display surface of the display device
30
.
In this construction, when an outer surface of the first resistive layer
12
is touched to be pressed, a touched portion of the first resistive layer
12
is brought into contact with a portion opposite thereto of the second resistive layer
13
, and a signal corresponding to the contact position (touched position) is generated.
In a practical construction, a transparent layer, for example, a Polyethylene Terephthalate film (hereinafter, referred to as “PET”
15
, is laminated on an outer surface of the first resistive layer
12
for protecting thereof, so the touching operation is implemented on this PET film
15
.
The first and second resistive layers
12
and
13
are combined at their peripheries by means of a sealing member
14
thereby making them dustproof and waterproof.
A light unit is added to the above-described display device
30
to illuminate the display surface brightly for making it easy to observe. A front light unit
20
to shine light on a front face (display surface) of the display device
30
is often used as the light unit in recent years.
FIG. 2
shows the touch panel
10
attached to the display device
30
having the front light unit
20
above described.
As shown in
FIG. 2
, the front light unit
20
has a light conductive plate
22
disposed facing the display surface of the display device
30
, and guides light emitted from a light source
21
located along the light source
21
toward the display surface of the display device
30
through the light conductive plate
22
. The light made incident on the display surface enters the display device
30
, is reflected at a bottom surface thereof, travels through the light conductive plate
22
and the touch panel
10
, and exits out (refer to an arrow indicated by a broken line in the figure), whereby an image on the display surface is visualized.
An array of prisms whose respective ridges are parallel to each other are formed on a surface opposite to a surface facing the display surface of the display device
30
so that, as described above, the light conductive plate
22
can guide light coming therein from its end toward the display surface of the display device
30
disposed therebelow.
However, in the conventional technology shown in
FIG. 2
, since the touch panel
10
and the front light unit
20
are constituted independent of each other, the touch panel
10
is easily subjected to the vibration and shock. And, because the touch panel
10
is required for strength against the vibration and shock when mounted on the device body, the thickness of the glass plate
16
needs to be increased so as to avoid damages on the glass plate
16
. However, there is a problem that the whole thickness (the depth) D of the display device
30
is increased when attached to the touch panel
10
. There is another problem that since the light conductive plate
22
is brought into a direct contact with the glass plate
16
, the light conductive plate
22
can be damaged or broken by the glass plate
16
when a vibration or shock is applied to the touch panel
10
.
Thus, a touch panel for a display device (the touch panel shown in FIG. 1 in the above-described Japanese Unexamined Patent Application Publication) was disclosed, where, as shown in
FIG. 3
, a second resistive layer
13
of a touch panel
10
is in a close contact with a surface of a light conductive plate
22
, on which an array of prisms are formed.
In this touch panel, a member (the glass plate
16
in
FIG. 2
) interposed between the light conductive plate
22
and the second resistive layer
13
of the touch panel
10
is eliminated, and the touch panel
10
is integrated with a front light unit
20
, and thus, the whole thickness D can be reduced when the touch panel and the front light unit are attached to a display device
30
. Further, the glass plate
16
in
FIG. 2
is not present, and thereby the problem that the light conductive plate
22
is damaged or broken by the glass plate when a vibration or shock is applied to the touch panel
10
can be solved.
However, there is a problem described below in the conventional technology shown in FIG.
3
.
Since the second resistive layer
13
is in a close contact with the surface of the light conductive plate
22
, on which the array of prisms are formed, as described above, a surface facing a first resistive layer
12
is also uneven corresponding to the surface of the array of prisms, and insulating dot spacers
11
are interposed between the uneven surface of the second resistive layer
13
and a flat surface of the first resistive layer
12
.
Thus, the linearity of the resistance value at each position on a touch panel operation surface (surface of the PET film
15
) is difficult to ensure, and errors occur easily in information obtained on the position.
In addition, there is a durability problem that projecting portions of the prisms formed on the one surface of the light conductive plate
22
and projecting portions of the second resistive layer
13
to cover the light conductive plate are easily damaged while the touch panel
10
is used.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a touch panel for a display device, which combines advantages of the conventional technologies shown in
FIGS. 2 and 3
that the whole thickness is not increased excessively when the touch panel is attached to the display device, the light conductive plate is not damaged or broken when a vibration or shock is applied to the touch panel, no errors occur in information obtained on the position, the touch panel operation surface does not become wavy, the display quality is not degraded, and that the durability is excellent.
According to the present invention, in a touch panel for a display device which is structured such that one resistive layer of a pair of resistive layers disposed facing each other across a plurality of insulating dot spacers is laid on a translucent flat plate, is disposed close to a display device such that the translucent flat plate is directed toward a display surface of the display device and that a front light unit comprising a light source and a light conductive plate to guide light emitted from the light source toward the display surface of the display device is interposed therebetween, and in which a signal is generated by touching an outer surface of the other resistive layer corresponding to a position touched, wherein the translucent flat plate is formed of a polyethylene terephthalate film, and the light conductive plate is integrally combined with an outer surface of the polyethyle
Asakawa Toshiaki
Kawashima Satoshi
Friedhofer Michael
Minebea Co. Ltd.
Nath & Associates PLLC
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