Computer graphics processing and selective visual display system – Display peripheral interface input device – Touch panel
Reexamination Certificate
1999-07-14
2001-10-30
Shalwala, Bipin (Department: 2673)
Computer graphics processing and selective visual display system
Display peripheral interface input device
Touch panel
C345S174000
Reexamination Certificate
active
06310614
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a touch-panel input device overlayed on a liquid crystal panel, CRT or the like. An operator presses the device in a position corresponding to displayed information. The device determines the position pressed and sends appropriate command input data to a processing device such as a personal computer. The source of pressure on the device can be from a pen, finger or the like. More specifically, the present invention relates to a touch-panel input device that achieves improved visibility by sealing a transparent insulative fluid between transparent plates.
In general, touch-panel input devices are found on the display screen of a liquid crystal panel, CRT, or the like where an operator can select information by touching an appropriate area of the display. The touch-panel input device reacts to pressure applied to a transparent surface to indicate a specific position according to the contents of the display. The touch-panel device detects the display position selected and generates corresponding command input data. The generated command input data is then sent to a processing device such as a personal computer.
Touch-panel input devices of this type generally contain a movable plate positioned over a substrate. The substrate and movable plate are constructed to maintain a gap between the movable plate and the substrate when they are overlayed. The substrate and movable plate have conductive layers on the surfaces that face each other across the insulative gap. The conductive layers are made from transparent materials to provide visual access to the display screen. However, the presence of air between the substrate and the movable plate creates a large refraction index differential. This large refraction index differential results in a transmittance efficiency of 80%, making the screen difficult to view.
The difficulty in viewing the display screen is addressed in touch-panel input devices such as in Japanese laid-open patent publication number 64-14630 and Japanese laid-open patent publication number 2-105916. These publications disclose a solution to the above difficulty by injecting a transparent, insulative fluid between the substrate and the movable plate. The fluid has a refraction index that is close to that of the materials used in the substrate and the movable plate, thus reducing reflectivity and improving transmittance.
Referring to FIG.
5
and
FIG. 6
, there is shown a conventional touch-panel input device
100
. A thin transparent plate
101
is a movable plate and transparent substrate
102
is a thick substrate that faces a display device (not shown). A frame-shaped spacer
105
is layered between transparent plate
101
and transparent substrate
102
to form a slight gap.
Transparent conductor layers
103
,
104
are composed of an Indium Tin Oxide (ITO) film or the like, printed on the facing surfaces of transparent plate
101
and transparent substrate
102
. The ITO film is printed on the facing surfaces with a uniform thickness. Leads
103
a,
103
b,
104
a
and
104
b
are also printed on these facing surfaces to provide electrical connections for transparent conductor layers
103
,
104
. A voltage generated at a contact point between transparent conductor layers
103
,
104
is measured on the electrical path provided by leads
103
a,
103
b,
104
a
and
104
b.
The measured voltage at the contact point enables detection of the position at which transparent plate
101
is pressed.
Transparent conductor layers
103
,
104
are usually separated by spacer
105
. Dot spacers
106
are printed on transparent conductor layer
104
at regular intervals sufficient to prevent light pressure applied to transparent plate
101
from causing accidental contact between the transparent conductor layers
103
,
104
. Dot spacers
106
are composed of an insulative composite resin such as epoxy resin. Dot spacers
106
augment the gap separation provided by spacer
105
to prevent position from being detected when transparent plate
101
is accidentally or lightly touched.
Spacer
105
is composed of a tacking agent
105
b
applied to upper and lower surfaces of a thin plate
105
a.
A sealed space between transparent conductor layers
103
,
104
and within spacer
105
is formed by tacking thin plate
105
a
to transparent plate
101
and transparent substrate
102
. Thin plate
105
a
is tacked to transparent plate
101
and transparent substrate
102
at the perimeters of transparent conductor layers
103
,
104
.
Transparent plate
101
can move horizontally (in the direction indicated by the arrow in
FIG. 6
) over tacking agent
105
b
while maintaining a sealed space between transparent conductor layers
103
,
104
. This configuration provides a close, tight contact between transparent plate
101
and spacer
105
, while at the same time permitting transparent plate
101
to move elastically over thin plate
105
a
in a horizontal direction. When pressure is applied to transparent plate
101
, the region surrounding the point of contact is uniformly flexed toward transparent substrate
102
. The flexure of transparent plate
101
remains uniform, even if the point of contact is near spacer
105
in a perimeter region of transparent plate
101
.
Once a sealed space between transparent conductor layers
103
,
104
is achieved, a transparent insulative fluid
107
is injected into the space. Transparent insulative fluid
107
has a refraction index that is relatively close to the refraction indices for the transparent conductor layers
103
,
104
. For example, ITO has a refraction index of 1.9, while silicon oil, an example of a transparent insulative fluid
107
, has a refraction index of 1.4.
Interposing transparent insulative fluid
107
between transparent conductor layers
103
,
104
reduces the amount of light reflected by touch-panel input device
100
when exposed to an illumination source (not shown) located above touch-panel input device
100
. Since transparent insulative fluid
107
has a refraction index relatively close to that of transparent conductor layers
103
,
104
, overall light transmittance increases to around 90%. The light reflected by touch-panel input device
100
is correspondingly reduced, thus significantly improving visibility of the display screen.
In this type of conventional touch-panel input device
100
, pressure is applied to transparent plate
101
to create contact between transparent conductor layer
104
and opposing transparent conductor layer
103
. The width of the gap between conductor layers
103
,
104
is kept small to provide reliable contact and other advantages. One means of keeping the gap width small is to interpose between transparent conductor layers
103
,
104
as a thin film. Transparent insulative fluid
107
then provides insulation between transparent conductor layers
103
,
104
with a small gap width. However, the applied pressure to transparent plate
101
needed to create contact between transparent conductor layers
103
,
104
increases significantly.
The increased pressure needed to create contact between transparent conductor layers
103
,
104
can be achieved by use of a dedicated input device such as a stylus pen. The stylus pen applies increased pressure per unit area which makes reliable input more consistent. However, the addition of a stylus pen further complicates device operation by increasing the number of parts and slowing user input. Also, the stylus pen can be lost, which makes the device difficult to operate.
In addition to requiring greater pressure, the use of a person's finger to operate the device results in greater contact area. A curved surface such as a person's finger having a curvature radius of, for example, 25 mm, creates a relatively broad area of contact when applied to transparent plate
101
. This broad area of contact requires increased pressure per unit area to assure contact between transparent conductor layers
103
,
104
. Such a large pressure requirement results in inadequate contact b
Maeda Toshifumi
Tanaka Hiroshi
Morrison Law Firm
Osorio Ricardo
Shalwala Bipin
SMK Corporation
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