Computer graphics processing and selective visual display system – Display peripheral interface input device – Touch panel
Reexamination Certificate
1999-10-14
2003-02-18
Chow, Dennis-Doon (Department: 2675)
Computer graphics processing and selective visual display system
Display peripheral interface input device
Touch panel
C345S174000, C178S018050, C341S034000
Reexamination Certificate
active
06522322
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a touch panel input device. Command input data is entered by pressing the surface of a transparent plate with a pen, finger, or the like. An electrical impulse is generated corresponding to the position of the pressure point and is sent to a processing device. More specifically, the present invention relates to a touch panel input device that enhances visibility by sealing a transparent insulative liquid between transparent plates. In general, touch panel input devices are found on the display screens of liquid crystal panels, CRTs, or the like. The operational surface of the touch panel input device is pressed while viewing the display information. The pressed position is detected and interpreted as command input data corresponding to the displayed content. The command input data is then sent to a processing device.
Touch panel input devices generally consist of a movable plate laminated over a substrate plate with an intervening insulative gap. Both the movable plate and the substrate plate have conductive layers covering their surfaces. The conductive surfaces are arraigned to face each other. The conductive surfaces are made from a transparent material which allows the underlying display screen to be viewed through them. There is a large difference between the refractive index of the air in the insulative gap and the refractive indices of the substrate and the movable plate. The difference in the refractive indices results in a transmittivity of only about 80% The reduction of the transmitted light makes the underlying display screen difficult to view.
Referring to
FIGS. 5 and 6
, a conventional touch panel input device
100
consists of a movable thin transparent plate
101
, and a thick transparent plate
102
that is mounted up against a display device (not shown.) The two transparent plates,
101
and
102
are laminated together with a slight gap using a frame-shaped spacer
105
.
Both facing surfaces of the transparent plates
101
and
102
, are coated with smooth transparent conductor layers
103
and
104
, of uniform thickness consisting of an indium tin oxide (ITO) film or other suitable transparent conductors. Leads
103
a
,
103
b
,
104
a
, and
104
b
are electrically connected on both sides of smooth transparent conductor layers
103
and
104
respectively. The voltage is read at a contact position between smooth transparent conductor layers
103
and
104
and the voltage corresponds to the pressed position on the surface of movable thin transparent plate
101
.
Smooth transparent conductor layers
103
and
104
are usually separated by a frame shaped spacer
105
. Dot spacers
106
which are composed of an insulative composite resin such as epoxy resin, are also affixed to transparent conductor layer
104
at appropriate intervals to prevent accidental contact between smooth transparent conductor layers
103
and
104
. Dot spacers
106
often prevent the pressed position from being detected if the radius of curvature of the pressing device, as is the case when using a finger, is large. This also prevents accidental input from being detected when a person holding a stylus accidentally touches the surface of touch panel input device
100
. This is referred to as a slip-of-the-hand operation.
The top and bottom surfaces of frame shaped spacer
105
are glued by an adhesive to the perimeter of smooth transparent conductor layers
103
and
104
, sealing in the space between smooth transparent conductor layers
103
and
104
. A transparent insulative liquid
107
is injected into the space between smooth transparent conductor layers
103
and
104
.The refractive index of the transparent insulative liquid
107
is closer to the refractive index of the smooth transparent conductor layers
103
and
104
than it is to the refractive index of air. Because the difference between the refractive indices of the transparent insulative liquid
107
and the smooth transparent conductive layers
103
and
104
is less than the difference between the refractive indices of air and the smooth transparent conductor layers
103
and
104
, the amount of light transmitted through the touch panel input device
100
is improved.
This difficulty is addressed in, for example, Japanese unexamined patent application publication number S64-14630(1989) and Japanese unexamined patent application publication number H2-105916 (1990), which disclose a touch panel input device in which a transparent, insulative liquid that has a refractive index that is relatively close to that of the substrate and movable plate, is injected between them and sealed. Use of an insulative liquid with a comparable refractive index both lowers reflectivity and improves transinittivity.
When an insulative liquid such as silicon oil is used, transmittivity can be increased to about 90%. The underlying display screen is much easier to read because it appears brighter and has less glare.
Unfortunately, while improving transmittivity, the introduction of the insulative liquid leads to other problems, especially when the touch panel input device is operated in a tilted position. When the touch panel input device is operated in a generally vertical orientation, the insulative liquid between the two plates settles downward under its own weight. This produces a near vacuum in the upper section, allowing the facing surfaces of the transparent plate and the transparent substrate to approach each other within several microns. The close proximity of the two plates leads to false command data input being sent to the processor, even though the screen is not being pressed.
In addition to the above problem, when the screen is pressed, it is more difficult to bring the moveable transparent plate in contact with transparent substrate, because of the presence of the insulative liquid. The insulative liquid increases the pressing force required to operate the device. Devices that increase the pressure by applying the force over a smaller area, such as a stylus pen, can be used to overcome this problem, but this solution does not help when operating the touch panel with a finger, as is often desirable. Because the force is spread out over a greater area when using a finger, the pressure applied to the moveable transparent plate is decreased making it difficult to detect the pressed position. Because of this, operations such as writing text, drawing figures, or dragging the cursor on the display screen using only a finger is very difficult.
OBJECTS AND SUMMARY OF THE INVENTION
In view of the above discussion, it is an object of the present invention to overcome the drawbacks of the prior art.
It is a further object of the present invention to provide a touch panel input device that utilizes a light pressing force, without malfunctioning, even if the device as a whole is tilted and even if the input is done with a finger.
Briefly stated, the present invention provides a transparent insulative liquid sealed between two transparent plates that are coated with transparent conductor layers on their mutually facing surfaces of a touch panel input device. The facing surface of at least one of the transparent plates is roughened. Because the conductor layer is applied directly over the roughened surface of the transparent plate, the conductor layer is also roughened. When the entire device is tilted, the insulative liquid settles downward allowing the upper conductor layers to come into contact with each other, but because the surface is roughened only the protrusions of the conductor layer make contact. The overall contact resistance does not decrease sufficiently to be interpreted as a pressing operation. When a pressing operation is made, the insulative liquid flows into the depressions created by the roughened surface of the conductor layer. Because the liquid is not interposed between conductor layers, sure contact is made, and the pressed position requires only a light pressing force.
According to an embodiment of the invention, there is provided a touch panel input d
Maeda Toshifumi
Sakurada Hidemasa
Tanaka Hiroshi
Chow Dennis-Doon
Darby & Darby
SMK Corporation
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